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* [BUG REPORT] Git does not correctly replay bisect log
@ 2018-12-04  9:51 Lukáš Krejčí
  2018-12-04 10:57 ` Lukáš Krejčí
  2018-12-04 11:04 ` Christian Couder
  0 siblings, 2 replies; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-04  9:51 UTC (permalink / raw)
  To: git

Executing git bisect replay reaches a different commit than
the one that is obtained by running the commands from the bisect log manually.

Distribution: Arch Linux
git: 2.19.2-1
perl: 5.28.1-1
pcre2: 10.32-1
expat: 2.2.6-1
perl-error: 0.17027-1
grep: 3.1-2
bash: 4.4.023-1

no system /etc/gitconfig is present
tried with no ~/.gitconfig

$ cat .git/config
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[remote "origin"]
        url = git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
        remote = origin
        merge = refs/heads/master

$ git fsck
Checking object directories: 100% (256/256), done.
warning in tag 5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 26791a8bcf0e6d33f43aef7682bdb555236d56de:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 9e734775f7c22d2f89943ad6c745571f1930105f:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 0397236d43e48e821cce5bbe6a80a1a56bb7cc3a:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag ebb5573ea8beaf000d4833735f3e53acb9af844c:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 06f6d9e2f140466eeb41e494e14167f90210f89d:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 701d7ecec3e0c6b4ab9bb824fd2b34be4da63b7e:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 733ad933f62e82ebc92fed988c7f0795e64dea62:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag c521cb0f10ef2bf28a18e1cc8adf378ccbbe5a19:
missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag a339981ec18d304f9efeb9ccf01b1f04302edf32:
missingTaggerEntry: invalid format - expected 'tagger' line
Checking objects: 100% (6428247/6428247), done.
Checking connectivity: 6369862, done.

$ cat /var/tmp/git-bisect.log
git bisect start
# bad: [5b394b2ddf0347bef56e50c69a58773c94343ff3] Linux 4.19-rc1
git bisect bad 5b394b2ddf0347bef56e50c69a58773c94343ff3
# good: [94710cac0ef4ee177a63b5227664b38c95bbf703] Linux 4.18
git bisect good 94710cac0ef4ee177a63b5227664b38c95bbf703
# bad: [54dbe75bbf1e189982516de179147208e90b5e45] Merge tag
'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
git bisect bad 54dbe75bbf1e189982516de179147208e90b5e45
# bad: [0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add
missing include file
git bisect bad 0a957467c5fd46142bc9c52758ffc552d4c5e2f7
# good: [958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch
'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 958f338e96f874a0d29442396d6adf9c1e17aa2d
# bad: [2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag
'acpi-4.19-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
git bisect bad 2c20443ec221dcb76484b30933593e8ecd836bbd
# bad: [c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag
'mtd/for-4.19' of git://git.infradead.org/linux-mtd
git bisect bad c2fc71c9b74c1e87336a27dba1a5edc69d2690f1
# bad: [b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make
blkg_root_lookup() work for queues in bypass mode
git bisect bad b86d865cb1cae1e61527ea0b8977078bbf694328
# bad: [1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
git bisect bad 1b0d274523df5ef1caedc834da055ff721e4d4f0

$ git status
On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

$ git log -1 --format=oneline
2595646791c319cadfdbf271563aac97d0843dc7 (HEAD -> master, tag:
v4.20-rc5, origin/master, origin/HEAD) Linux 4.20-rc5

$ git bisect replay /var/tmp/git-bisect.log
We are not bisecting.
Bisecting: a merge base must be tested
[d72e90f33aa4709ebecc5005562f52335e106a60] Linux 4.18-rc6

$ git log -1 --format=oneline
d72e90f33aa4709ebecc5005562f52335e106a60 (HEAD, tag: v4.18-rc6) Linux 4.18-rc6





Running the commands from the bisect log manually, however:

$ git bisect reset
Checking out files: 100% (18326/18326), done.
Previous HEAD position was d72e90f33aa4 Linux 4.18-rc6
Switched to branch 'master'
Your branch is up to date with 'origin/master'.

$ . /var/tmp/git-bisect.log
Bisecting: 6112 revisions left to test after this (roughly 13 steps)
[54dbe75bbf1e189982516de179147208e90b5e45] Merge tag
'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
Bisecting: 3881 revisions left to test after this (roughly 12 steps)
[0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add missing include file
Bisecting: 1595 revisions left to test after this (roughly 11 steps)
[958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch 'l1tf-final'
of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Bisecting: 854 revisions left to test after this (roughly 10 steps)
[2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag 'acpi-4.19-rc1'
of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Bisecting: 352 revisions left to test after this (roughly 9 steps)
[c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag 'mtd/for-4.19' of
git://git.infradead.org/linux-mtd
Bisecting: 193 revisions left to test after this (roughly 8 steps)
[b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make
blkg_root_lookup() work for queues in bypass mode
Bisecting: 97 revisions left to test after this (roughly 7 steps)
[1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
Bisecting: 47 revisions left to test after this (roughly 6 steps)
[6dad38d38f20c0c8a84b5ae4f23c62b2c8758ec5] null_blk: move shared
definitions to header file

$ git log -1 --format=oneline
6dad38d38f20c0c8a84b5ae4f23c62b2c8758ec5 (HEAD) null_blk: move shared
definitions to header file

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04  9:51 [BUG REPORT] Git does not correctly replay bisect log Lukáš Krejčí
@ 2018-12-04 10:57 ` Lukáš Krejčí
  2018-12-04 11:04 ` Christian Couder
  1 sibling, 0 replies; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-04 10:57 UTC (permalink / raw)
  To: git

(I'm sorry about the formatting, here's the message again.)

Executing git bisect replay reaches a different commit than
the one that is obtained by running the commands from the bisect log manually.

Distribution: Arch Linux
git: 2.19.2-1
perl: 5.28.1-1
pcre2: 10.32-1
expat: 2.2.6-1
perl-error: 0.17027-1
grep: 3.1-2
bash: 4.4.023-1

no system /etc/gitconfig is present
tried with no ~/.gitconfig

$ cat .git/config 
[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[remote "origin"]
        url = git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
        remote = origin
        merge = refs/heads/master

$ git fsck
Checking object directories: 100% (256/256), done.
warning in tag 5dc01c595e6c6ec9ccda4f6f69c131c0dd945f8c: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 26791a8bcf0e6d33f43aef7682bdb555236d56de: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 9e734775f7c22d2f89943ad6c745571f1930105f: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 0397236d43e48e821cce5bbe6a80a1a56bb7cc3a: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag ebb5573ea8beaf000d4833735f3e53acb9af844c: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 06f6d9e2f140466eeb41e494e14167f90210f89d: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 701d7ecec3e0c6b4ab9bb824fd2b34be4da63b7e: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag 733ad933f62e82ebc92fed988c7f0795e64dea62: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag c521cb0f10ef2bf28a18e1cc8adf378ccbbe5a19: missingTaggerEntry: invalid format - expected 'tagger' line
warning in tag a339981ec18d304f9efeb9ccf01b1f04302edf32: missingTaggerEntry: invalid format - expected 'tagger' line
Checking objects: 100% (6428247/6428247), done.
Checking connectivity: 6369862, done.

$ cat /var/tmp/git-bisect.log
git bisect start
# bad: [5b394b2ddf0347bef56e50c69a58773c94343ff3] Linux 4.19-rc1
git bisect bad 5b394b2ddf0347bef56e50c69a58773c94343ff3
# good: [94710cac0ef4ee177a63b5227664b38c95bbf703] Linux 4.18
git bisect good 94710cac0ef4ee177a63b5227664b38c95bbf703
# bad: [54dbe75bbf1e189982516de179147208e90b5e45] Merge tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
git bisect bad 54dbe75bbf1e189982516de179147208e90b5e45
# bad: [0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add missing include file
git bisect bad 0a957467c5fd46142bc9c52758ffc552d4c5e2f7
# good: [958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 958f338e96f874a0d29442396d6adf9c1e17aa2d
# bad: [2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag 'acpi-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
git bisect bad 2c20443ec221dcb76484b30933593e8ecd836bbd
# bad: [c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag 'mtd/for-4.19' of git://git.infradead.org/linux-mtd
git bisect bad c2fc71c9b74c1e87336a27dba1a5edc69d2690f1
# bad: [b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make blkg_root_lookup() work for queues in bypass mode
git bisect bad b86d865cb1cae1e61527ea0b8977078bbf694328
# bad: [1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
git bisect bad 1b0d274523df5ef1caedc834da055ff721e4d4f0

$ git status
On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

$ git log -1 --format=oneline
2595646791c319cadfdbf271563aac97d0843dc7 (HEAD -> master, tag: v4.20-rc5, origin/master, origin/HEAD) Linux 4.20-rc5

$ git bisect replay /var/tmp/git-bisect.log 
We are not bisecting.
Bisecting: a merge base must be tested
[d72e90f33aa4709ebecc5005562f52335e106a60] Linux 4.18-rc6

$ git log -1 --format=oneline
d72e90f33aa4709ebecc5005562f52335e106a60 (HEAD, tag: v4.18-rc6) Linux 4.18-rc6





# Running the commands from the bisect log manually, however:

$ git bisect reset
Checking out files: 100% (18326/18326), done.
Previous HEAD position was d72e90f33aa4 Linux 4.18-rc6
Switched to branch 'master'
Your branch is up to date with 'origin/master'.

$ . /var/tmp/git-bisect.log 
Bisecting: 6112 revisions left to test after this (roughly 13 steps)
[54dbe75bbf1e189982516de179147208e90b5e45] Merge tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
Bisecting: 3881 revisions left to test after this (roughly 12 steps)
[0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add missing include file
Bisecting: 1595 revisions left to test after this (roughly 11 steps)
[958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Bisecting: 854 revisions left to test after this (roughly 10 steps)
[2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag 'acpi-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Bisecting: 352 revisions left to test after this (roughly 9 steps)
[c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag 'mtd/for-4.19' of git://git.infradead.org/linux-mtd
Bisecting: 193 revisions left to test after this (roughly 8 steps)
[b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make blkg_root_lookup() work for queues in bypass mode
Bisecting: 97 revisions left to test after this (roughly 7 steps)
[1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
Bisecting: 47 revisions left to test after this (roughly 6 steps)
[6dad38d38f20c0c8a84b5ae4f23c62b2c8758ec5] null_blk: move shared definitions to header file

$ git log -1 --format=oneline
6dad38d38f20c0c8a84b5ae4f23c62b2c8758ec5 (HEAD) null_blk: move shared definitions to header file


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04  9:51 [BUG REPORT] Git does not correctly replay bisect log Lukáš Krejčí
  2018-12-04 10:57 ` Lukáš Krejčí
@ 2018-12-04 11:04 ` Christian Couder
  2018-12-04 11:20   ` Lukáš Krejčí
  1 sibling, 1 reply; 10+ messages in thread
From: Christian Couder @ 2018-12-04 11:04 UTC (permalink / raw)
  To: lskrejci; +Cc: git

On Tue, Dec 4, 2018 at 10:53 AM Lukáš Krejčí <lskrejci@gmail.com> wrote:
>
> Executing git bisect replay reaches a different commit than
> the one that is obtained by running the commands from the bisect log manually.


> $ git bisect replay /var/tmp/git-bisect.log
> We are not bisecting.
> Bisecting: a merge base must be tested
> [d72e90f33aa4709ebecc5005562f52335e106a60] Linux 4.18-rc6

Merge bases are tested only when the good commit is not an ancestor of
the bad commit. If this didn't happen when the log was recorded, it
shouldn't happen when it is replayed.

Here it seems that this is happening at the beginning of the replay.
Perhaps git bisect replay is taking into account the current
branch/commit though it shouldn't.

I wonder if this would happen if the current branch/commit has the
good commit as an ancestor.

Could you try to check that? And first could you give us the output of:

git merge-base 5b394b2ddf0347bef56e50c69a58773c94343ff3
94710cac0ef4ee177a63b5227664b38c95bbf703

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04 11:04 ` Christian Couder
@ 2018-12-04 11:20   ` Lukáš Krejčí
  2018-12-04 12:01     ` Christian Couder
  0 siblings, 1 reply; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-04 11:20 UTC (permalink / raw)
  To: Christian Couder; +Cc: git

On Tue, 2018-12-04 at 12:04 +0100, Christian Couder wrote:
> 
> Could you try to check that? And first could you give us the output of:
> 
> git merge-base 5b394b2ddf0347bef56e50c69a58773c94343ff3
> 94710cac0ef4ee177a63b5227664b38c95bbf703

$ git merge-base 5b394b2ddf0347bef56e50c69a58773c94343ff3 94710cac0ef4ee177a63b5227664b38c95bbf703
94710cac0ef4ee177a63b5227664b38c95bbf703
$ git log -1 --format=oneline 94710cac0ef4ee177a63b5227664b38c95bbf703
94710cac0ef4ee177a63b5227664b38c95bbf703 (tag: v4.18) Linux 4.18


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04 11:20   ` Lukáš Krejčí
@ 2018-12-04 12:01     ` Christian Couder
  2018-12-04 13:36       ` Lukáš Krejčí
  2018-12-06 14:43       ` Lukáš Krejčí
  0 siblings, 2 replies; 10+ messages in thread
From: Christian Couder @ 2018-12-04 12:01 UTC (permalink / raw)
  To: lskrejci; +Cc: git

On Tue, Dec 4, 2018 at 12:20 PM Lukáš Krejčí <lskrejci@gmail.com> wrote:
>
> On Tue, 2018-12-04 at 12:04 +0100, Christian Couder wrote:
> >
> > Could you try to check that? And first could you give us the output of:
> >
> > git merge-base 5b394b2ddf0347bef56e50c69a58773c94343ff3
> > 94710cac0ef4ee177a63b5227664b38c95bbf703
>
> $ git merge-base 5b394b2ddf0347bef56e50c69a58773c94343ff3 94710cac0ef4ee177a63b5227664b38c95bbf703
> 94710cac0ef4ee177a63b5227664b38c95bbf703
> $ git log -1 --format=oneline 94710cac0ef4ee177a63b5227664b38c95bbf703
> 94710cac0ef4ee177a63b5227664b38c95bbf703 (tag: v4.18) Linux 4.18

94710cac0ef4ee177a63b5227664b38c95bbf703 is the good commit that was
initially given. This means that the good commit
94710cac0ef4ee177a63b5227664b38c95bbf703 is an ancestor of the bad
commit 5b394b2ddf0347bef56e50c69a58773c94343ff3 i and there should be
no reason to test a merge base when replaying.

After testing on my machine, it seems that the problem is not
happening at the beginning of the replay.

To debug I think it would be interesting to see the output of the
following commands just before we get different results:

git for-each-ref 'refs/bisect/*'

and

git log -1 --format=oneline

in the case we are using `git bisect replay` and in the case we are
running the commands from the bisect log manually.

(You might need to temporarily remove the last command from the bisect
log to do that.)

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04 12:01     ` Christian Couder
@ 2018-12-04 13:36       ` Lukáš Krejčí
  2018-12-06 14:43       ` Lukáš Krejčí
  1 sibling, 0 replies; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-04 13:36 UTC (permalink / raw)
  To: Christian Couder; +Cc: git

On Tue, 2018-12-04 at 13:01 +0100, Christian Couder wrote:
> To debug I think it would be interesting to see the output of the
> following commands just before we get different results:
> 
> git for-each-ref 'refs/bisect/*'
> 
> and
> 
> git log -1 --format=oneline
> 

I placed the following snippet at the end of the loop in bisect_replay():
echo "COMMAND: '$git' '$bisect' '$command' '$rev'"		
git for-each-ref 'refs/bisect/*'
echo "current HEAD: $(git log -1 --format=oneline)"
echo "---"

$ env GIT_TRACE=0 git bisect replay /var/tmp/git-bisect.log 

We are not bisecting.
COMMAND: 'git' 'bisect' 'start' ''
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' '5b394b2ddf0347bef56e50c69a58773c94343ff3'
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'good' '94710cac0ef4ee177a63b5227664b38c95bbf703'
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' '54dbe75bbf1e189982516de179147208e90b5e45'
54dbe75bbf1e189982516de179147208e90b5e45 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' '0a957467c5fd46142bc9c52758ffc552d4c5e2f7'
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'good' '958f338e96f874a0d29442396d6adf9c1e17aa2d'
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' '2c20443ec221dcb76484b30933593e8ecd836bbd'
2c20443ec221dcb76484b30933593e8ecd836bbd commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' 'c2fc71c9b74c1e87336a27dba1a5edc69d2690f1'
c2fc71c9b74c1e87336a27dba1a5edc69d2690f1 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' 'b86d865cb1cae1e61527ea0b8977078bbf694328'
b86d865cb1cae1e61527ea0b8977078bbf694328 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
COMMAND: 'git' 'bisect' 'bad' '1b0d274523df5ef1caedc834da055ff721e4d4f0'
1b0d274523df5ef1caedc834da055ff721e4d4f0 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
Bisecting: a merge base must be tested
[1e4b044d22517cae7047c99038abb444423243ca] Linux 4.18-rc4







# I placed git for-each-ref 'refs/bisect/*' after each command in the file:

$ . /var/tmp/git-bisect.log 
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
Bisecting: 6112 revisions left to test after this (roughly 13 steps)
[54dbe75bbf1e189982516de179147208e90b5e45] Merge tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
Bisecting: 3881 revisions left to test after this (roughly 12 steps)
[0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add missing include file
54dbe75bbf1e189982516de179147208e90b5e45 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
Bisecting: 1595 revisions left to test after this (roughly 11 steps)
[958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
Bisecting: 854 revisions left to test after this (roughly 10 steps)
[2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag 'acpi-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
Bisecting: 352 revisions left to test after this (roughly 9 steps)
[c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag 'mtd/for-4.19' of git://git.infradead.org/linux-mtd
2c20443ec221dcb76484b30933593e8ecd836bbd commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
Bisecting: 193 revisions left to test after this (roughly 8 steps)
[b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make blkg_root_lookup() work for queues in bypass mode
c2fc71c9b74c1e87336a27dba1a5edc69d2690f1 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
Bisecting: 97 revisions left to test after this (roughly 7 steps)
[1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
b86d865cb1cae1e61527ea0b8977078bbf694328 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
Bisecting: 47 revisions left to test after this (roughly 6 steps)
[6dad38d38f20c0c8a84b5ae4f23c62b2c8758ec5] null_blk: move shared definitions to header file
1b0d274523df5ef1caedc834da055ff721e4d4f0 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d








Here is the output of the first command with GIT_TRACE on.

$ env GIT_TRACE=1 git bisect replay /var/tmp/git-bisect.log 
14:30:26.859355 git.c:659               trace: exec: git-bisect replay /var/tmp/git-bisect.log
14:30:26.859422 run-command.c:643       trace: run_command: git-bisect replay /var/tmp/git-bisect.log
14:30:26.893410 git.c:415               trace: built-in: git rev-parse --git-dir
14:30:26.898676 git.c:415               trace: built-in: git rev-parse --show-cdup
14:30:26.906487 git.c:415               trace: built-in: git rev-parse --git-path objects
We are not bisecting.
14:30:26.928736 git.c:415               trace: built-in: git rev-parse --sq-quote
14:30:26.935080 git.c:415               trace: built-in: git rev-parse --is-bare-repository
14:30:26.941601 git.c:415               trace: built-in: git symbolic-ref -q HEAD
14:30:26.949947 git.c:415               trace: built-in: git bisect--helper --bisect-clean-state
14:30:26.961001 git.c:415               trace: built-in: git rev-parse --sq-quote
14:30:26.970945 git.c:415               trace: built-in: git show-ref -q --verify refs/bisect/bad
14:30:26.979838 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/good-*'
COMMAND: 'git' 'bisect' 'start' ''
14:30:26.989878 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
14:30:26.997573 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.012658 git.c:415               trace: built-in: git bisect--helper --write-terms bad good
14:30:27.021663 git.c:415               trace: built-in: git update-ref refs/bisect/bad 5b394b2ddf0347bef56e50c69a58773c94343ff3
14:30:27.032023 git.c:415               trace: built-in: git show-branch 5b394b2ddf0347bef56e50c69a58773c94343ff3
COMMAND: 'git' 'bisect' 'bad' '5b394b2ddf0347bef56e50c69a58773c94343ff3'
14:30:27.045300 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
14:30:27.055905 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.069302 git.c:415               trace: built-in: git update-ref refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703 94710cac0ef4ee177a63b5227664b38c95bbf703
14:30:27.080205 git.c:415               trace: built-in: git show-branch 94710cac0ef4ee177a63b5227664b38c95bbf703
COMMAND: 'git' 'bisect' 'good' '94710cac0ef4ee177a63b5227664b38c95bbf703'
14:30:27.091229 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
5b394b2ddf0347bef56e50c69a58773c94343ff3 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
14:30:27.101268 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.108474 git.c:415               trace: built-in: git update-ref refs/bisect/bad 54dbe75bbf1e189982516de179147208e90b5e45
14:30:27.117641 git.c:415               trace: built-in: git show-branch 54dbe75bbf1e189982516de179147208e90b5e45
COMMAND: 'git' 'bisect' 'bad' '54dbe75bbf1e189982516de179147208e90b5e45'
14:30:27.126344 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
54dbe75bbf1e189982516de179147208e90b5e45 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
14:30:27.135195 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.143550 git.c:415               trace: built-in: git update-ref refs/bisect/bad 0a957467c5fd46142bc9c52758ffc552d4c5e2f7
14:30:27.151005 git.c:415               trace: built-in: git show-branch 0a957467c5fd46142bc9c52758ffc552d4c5e2f7
COMMAND: 'git' 'bisect' 'bad' '0a957467c5fd46142bc9c52758ffc552d4c5e2f7'
14:30:27.157688 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
14:30:27.163749 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.171138 git.c:415               trace: built-in: git update-ref refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d 958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.177118 git.c:415               trace: built-in: git show-branch 958f338e96f874a0d29442396d6adf9c1e17aa2d
COMMAND: 'git' 'bisect' 'good' '958f338e96f874a0d29442396d6adf9c1e17aa2d'
14:30:27.186531 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
0a957467c5fd46142bc9c52758ffc552d4c5e2f7 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.199439 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.210832 git.c:415               trace: built-in: git update-ref refs/bisect/bad 2c20443ec221dcb76484b30933593e8ecd836bbd
14:30:27.219812 git.c:415               trace: built-in: git show-branch 2c20443ec221dcb76484b30933593e8ecd836bbd
COMMAND: 'git' 'bisect' 'bad' '2c20443ec221dcb76484b30933593e8ecd836bbd'
14:30:27.228918 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
2c20443ec221dcb76484b30933593e8ecd836bbd commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.237583 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.246265 git.c:415               trace: built-in: git update-ref refs/bisect/bad c2fc71c9b74c1e87336a27dba1a5edc69d2690f1
14:30:27.257213 git.c:415               trace: built-in: git show-branch c2fc71c9b74c1e87336a27dba1a5edc69d2690f1
COMMAND: 'git' 'bisect' 'bad' 'c2fc71c9b74c1e87336a27dba1a5edc69d2690f1'
14:30:27.268181 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
c2fc71c9b74c1e87336a27dba1a5edc69d2690f1 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.279037 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.287349 git.c:415               trace: built-in: git update-ref refs/bisect/bad b86d865cb1cae1e61527ea0b8977078bbf694328
14:30:27.293680 git.c:415               trace: built-in: git show-branch b86d865cb1cae1e61527ea0b8977078bbf694328
COMMAND: 'git' 'bisect' 'bad' 'b86d865cb1cae1e61527ea0b8977078bbf694328'
14:30:27.301385 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
b86d865cb1cae1e61527ea0b8977078bbf694328 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.307179 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.312767 git.c:415               trace: built-in: git update-ref refs/bisect/bad 1b0d274523df5ef1caedc834da055ff721e4d4f0
14:30:27.318559 git.c:415               trace: built-in: git show-branch 1b0d274523df5ef1caedc834da055ff721e4d4f0
COMMAND: 'git' 'bisect' 'bad' '1b0d274523df5ef1caedc834da055ff721e4d4f0'
14:30:27.323911 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/*'
1b0d274523df5ef1caedc834da055ff721e4d4f0 commit refs/bisect/bad
94710cac0ef4ee177a63b5227664b38c95bbf703 commit refs/bisect/good-94710cac0ef4ee177a63b5227664b38c95bbf703
958f338e96f874a0d29442396d6adf9c1e17aa2d commit refs/bisect/good-958f338e96f874a0d29442396d6adf9c1e17aa2d
14:30:27.329725 git.c:415               trace: built-in: git log -1 --format=oneline
current HEAD: 2595646791c319cadfdbf271563aac97d0843dc7 Linux 4.20-rc5
---
14:30:27.332326 git.c:415               trace: built-in: git show-ref -q --verify refs/bisect/bad
14:30:27.342139 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/good-*'
14:30:27.348466 git.c:415               trace: built-in: git show-ref -q --verify refs/bisect/bad
14:30:27.355160 git.c:415               trace: built-in: git for-each-ref 'refs/bisect/good-*'
14:30:27.364281 git.c:415               trace: built-in: git bisect--helper --next-all
Bisecting: a merge base must be tested
14:30:27.491498 run-command.c:643       trace: run_command: git checkout -q 1e4b044d22517cae7047c99038abb444423243ca --
14:30:27.497822 git.c:415               trace: built-in: git checkout -q 1e4b044d22517cae7047c99038abb444423243ca --
14:30:55.290141 run-command.c:643       trace: run_command: git show-branch 1e4b044d22517cae7047c99038abb444423243ca
14:30:55.292168 git.c:415               trace: built-in: git show-branch 1e4b044d22517cae7047c99038abb444423243ca
[1e4b044d22517cae7047c99038abb444423243ca] Linux 4.18-rc4


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-04 12:01     ` Christian Couder
  2018-12-04 13:36       ` Lukáš Krejčí
@ 2018-12-06 14:43       ` Lukáš Krejčí
  2018-12-06 16:31         ` Christian Couder
  1 sibling, 1 reply; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-06 14:43 UTC (permalink / raw)
  To: Christian Couder; +Cc: git

Hello again,

after looking into this today, I'm not sure if this can be considered a
bug - it's just that I expected Git to check out the exact commit to
test that was there before resetting the bisect. That made me uncertain
whether Git restored the correct state.

When I looked at what Git actually does, it became clear that the
behavior is not incorrect but perhaps a bit surprising.

When Git replays the bisect log, it only updates refs/bisect/bad,
refs/bisect/good-*, refs/bisect/skip-* and reconstructs the log in
.git/BISECT_LOG. After that check_good_are_ancestors_of_bad() verifies
that all good commits are ancestors of the bad commit, and if not, the
message "Bisecting: a merge base must be tested" is printed and the
branch is switched to the merge base of the bad and all the good
commits.

Basically, some state is lost because Git "forgot" the first good
commit from the log already was an ancestor of the first bad one.
In other words, it's as if I just started the bisect with the following
commands and just pasted the whole bisect log to .git/BISECT_LOG:

$ git bisect start
$ git bisect good 94710cac0ef4ee177a63b5227664b38c95bbf703
$ git bisect good 958f338e96f874a0d29442396d6adf9c1e17aa2d
$ git bisect bad 1b0d274523df5ef1caedc834da055ff721e4d4f0
Bisecting: a merge base must be tested
[1e4b044d22517cae7047c99038abb444423243ca] Linux 4.18-rc4

(here's the full bisect log again for reference)
git bisect start
# bad: [5b394b2ddf0347bef56e50c69a58773c94343ff3] Linux 4.19-rc1
git bisect bad 5b394b2ddf0347bef56e50c69a58773c94343ff3
# good: [94710cac0ef4ee177a63b5227664b38c95bbf703] Linux 4.18
git bisect good 94710cac0ef4ee177a63b5227664b38c95bbf703
# bad: [54dbe75bbf1e189982516de179147208e90b5e45] Merge tag 'drm-next-2018-08-15' of git://anongit.freedesktop.org/drm/drm
git bisect bad 54dbe75bbf1e189982516de179147208e90b5e45
# bad: [0a957467c5fd46142bc9c52758ffc552d4c5e2f7] x86: i8259: Add missing include file
git bisect bad 0a957467c5fd46142bc9c52758ffc552d4c5e2f7
# good: [958f338e96f874a0d29442396d6adf9c1e17aa2d] Merge branch 'l1tf-final' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 958f338e96f874a0d29442396d6adf9c1e17aa2d
# bad: [2c20443ec221dcb76484b30933593e8ecd836bbd] Merge tag 'acpi-4.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
git bisect bad 2c20443ec221dcb76484b30933593e8ecd836bbd
# bad: [c2fc71c9b74c1e87336a27dba1a5edc69d2690f1] Merge tag 'mtd/for-4.19' of git://git.infradead.org/linux-mtd
git bisect bad c2fc71c9b74c1e87336a27dba1a5edc69d2690f1
# bad: [b86d865cb1cae1e61527ea0b8977078bbf694328] blkcg: Make blkg_root_lookup() work for queues in bypass mode
git bisect bad b86d865cb1cae1e61527ea0b8977078bbf694328
# bad: [1b0d274523df5ef1caedc834da055ff721e4d4f0] nvmet: don't use uuid_le type
git bisect bad 1b0d274523df5ef1caedc834da055ff721e4d4f0

And indeed, marking the merge base as good switches to the correct
commit after the bisect. Marking it as bad will fail, so at least you
can't make a mistake after replaying the bisect log:
$ git bisect bad
The merge base 1e4b044d22517cae7047c99038abb444423243ca is bad.
This means the bug has been fixed between 1e4b044d22517cae7047c99038abb444423243ca and [94710cac0ef4ee177a63b5227664b38c95bbf703 958f338e96f874a0d29442396d6adf9c1e17aa2d].

Once again, I'm sorry for the noise. I guess it wasn't clear from the
man page that something like this could happen and that made me think
that this was a bug.


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-06 14:43       ` Lukáš Krejčí
@ 2018-12-06 16:31         ` Christian Couder
  2018-12-06 17:30           ` Lukáš Krejčí
  0 siblings, 1 reply; 10+ messages in thread
From: Christian Couder @ 2018-12-06 16:31 UTC (permalink / raw)
  To: lskrejci; +Cc: git

Hi,

On Thu, Dec 6, 2018 at 3:43 PM Lukáš Krejčí <lskrejci@gmail.com> wrote:
>
> Hello again,
>
> after looking into this today, I'm not sure if this can be considered a
> bug - it's just that I expected Git to check out the exact commit to
> test that was there before resetting the bisect. That made me uncertain
> whether Git restored the correct state.
>
> When I looked at what Git actually does, it became clear that the
> behavior is not incorrect but perhaps a bit surprising.

Yeah, I agree. I suspect, but I am not sure, that the difference of
behavior is because in one case we only check merge bases once at the
beginning (maybe because the BISECT_ANCESTORS_OK file always exists)
while in the other case we check them more than once during the
bisection. I haven't had time to look closely at this, but I would
like to.

> When Git replays the bisect log, it only updates refs/bisect/bad,
> refs/bisect/good-*, refs/bisect/skip-* and reconstructs the log in
> .git/BISECT_LOG. After that check_good_are_ancestors_of_bad() verifies
> that all good commits are ancestors of the bad commit, and if not, the
> message "Bisecting: a merge base must be tested" is printed and the
> branch is switched to the merge base of the bad and all the good
> commits.

I am not sure if you are talking about running `git bisect replay` or
sourcing the log in the above.

> Basically, some state is lost because Git "forgot" the first good
> commit from the log already was an ancestor of the first bad one.

The BISECT_ANCESTORS_OK file should be there to avoid forgetting that
we already checked the merge bases.

> In other words, it's as if I just started the bisect with the following
> commands and just pasted the whole bisect log to .git/BISECT_LOG:
>
> $ git bisect start
> $ git bisect good 94710cac0ef4ee177a63b5227664b38c95bbf703
> $ git bisect good 958f338e96f874a0d29442396d6adf9c1e17aa2d
> $ git bisect bad 1b0d274523df5ef1caedc834da055ff721e4d4f0
> Bisecting: a merge base must be tested
> [1e4b044d22517cae7047c99038abb444423243ca] Linux 4.18-rc4

Yeah, when we start a new bisection the BISECT_ANCESTORS_OK file
should be erased if it exists, while it shouldn't be erased when we
are already in the middle of an existing bisection.

[...]

> And indeed, marking the merge base as good switches to the correct
> commit after the bisect. Marking it as bad will fail, so at least you
> can't make a mistake after replaying the bisect log:
> $ git bisect bad
> The merge base 1e4b044d22517cae7047c99038abb444423243ca is bad.
> This means the bug has been fixed between 1e4b044d22517cae7047c99038abb444423243ca and [94710cac0ef4ee177a63b5227664b38c95bbf703 958f338e96f874a0d29442396d6adf9c1e17aa2d].

Yeah, I think this works as expected.

> Once again, I'm sorry for the noise. I guess it wasn't clear from the
> man page that something like this could happen and that made me think
> that this was a bug.

No reason to be sorry, there might still be a bug related to the
BISECT_ANCESTORS_OK file or something. I hope I can take a look at
this more closely soon.

Thanks for your report and your work on this,
Christian.

^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-06 16:31         ` Christian Couder
@ 2018-12-06 17:30           ` Lukáš Krejčí
  2018-12-06 23:02             ` Christian Couder
  0 siblings, 1 reply; 10+ messages in thread
From: Lukáš Krejčí @ 2018-12-06 17:30 UTC (permalink / raw)
  To: Christian Couder; +Cc: git

On Thu, 2018-12-06 at 17:31 +0100, Christian Couder wrote:
> > When Git replays the bisect log, it only updates refs/bisect/bad,
> > refs/bisect/good-*, refs/bisect/skip-* and reconstructs the log in
> > .git/BISECT_LOG. After that check_good_are_ancestors_of_bad() verifies
> > that all good commits are ancestors of the bad commit, and if not, the
> > message "Bisecting: a merge base must be tested" is printed and the
> > branch is switched to the merge base of the bad and all the good
> > commits.
> 
> I am not sure if you are talking about running `git bisect replay` or
> sourcing the log in the above.

I am talking about `git bisect replay`. The shell script, as far as I
can see, only updates the references (ref/bisect/*) and never checks if
the revisions marked as 'good' are ancestors of the 'bad' one.
Therefore, $GIT_DIR/BISECT_ANCESTORS_OK file is never created.

The first time the ancestors are checked is in the helper (`git-bisect-
-help --next-all`) that has only limited information from refs/bisect*.


^ permalink raw reply	[flat|nested] 10+ messages in thread

* Re: [BUG REPORT] Git does not correctly replay bisect log
  2018-12-06 17:30           ` Lukáš Krejčí
@ 2018-12-06 23:02             ` Christian Couder
  0 siblings, 0 replies; 10+ messages in thread
From: Christian Couder @ 2018-12-06 23:02 UTC (permalink / raw)
  To: lskrejci; +Cc: git

On Thu, Dec 6, 2018 at 6:30 PM Lukáš Krejčí <lskrejci@gmail.com> wrote:
>
> I am talking about `git bisect replay`. The shell script, as far as I
> can see, only updates the references (ref/bisect/*) and never checks if
> the revisions marked as 'good' are ancestors of the 'bad' one.
> Therefore, $GIT_DIR/BISECT_ANCESTORS_OK file is never created.

Indeed `git bisect replay` first only updates the references
(ref/bisect/*) according to all the "git bisect {good,bad}"
instructions it finds in the log it is passed. After doing that
though, before exiting, it calls `bisect_auto_next` which calls
`bisect_next` which calls `git bisect--helper --next-all` which checks
the merge bases.

I think it is a bug.

`git bisect replay` is right to only update the references
(ref/bisect/*) and not to compute and checkout the best commit to test
at each step except at the end, but it should probably just create the
$GIT_DIR/BISECT_ANCESTORS_OK file if more than one bisection step has
been performed (because the merge bases are checked as part of the
first bisection step only).

> The first time the ancestors are checked is in the helper (`git-bisect-
> -help --next-all`) that has only limited information from refs/bisect*.

`git-bisect--helper --next-all` knows how to get refs/bisect*
information, otherwise it couldn't decide which is the next best
commit to test.

Thanks for your help in debugging this,
Christian.

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, back to index

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-12-04  9:51 [BUG REPORT] Git does not correctly replay bisect log Lukáš Krejčí
2018-12-04 10:57 ` Lukáš Krejčí
2018-12-04 11:04 ` Christian Couder
2018-12-04 11:20   ` Lukáš Krejčí
2018-12-04 12:01     ` Christian Couder
2018-12-04 13:36       ` Lukáš Krejčí
2018-12-06 14:43       ` Lukáš Krejčí
2018-12-06 16:31         ` Christian Couder
2018-12-06 17:30           ` Lukáš Krejčí
2018-12-06 23:02             ` Christian Couder

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