Rebase doesn't restore branch pointer back on out of memory

Rebase doesn't restore branch pointer back on out of memory

[Alexander Kostikov]

Hi,

I'd like to report a bug in git (observed on git version 1.7.11.msysgit.1).
When you do a rebase and it fails due to out of memory exception,
rebased branch pointer is changed but commits are not rebased. That
makes commits that you are rebasing unreachable (except via reflog):

» git lg
* 4c60761 - (origin/master, origin/HEAD, master) ...

» git rebase master sql_script
First, rewinding head to replay your work on top of it...
fatal: Out of memory? mmap failed: No error

» git lg
* 4c60761 - (HEAD, origin/master, origin/HEAD, sql_script, master) ...

» git reflog sql_script
4c60761 sql_script@{0}: rebase finished: refs/heads/sql_script onto
4c60761303fccbb0860b28e8094ad17ae8b01d07
13555ed sql_script@{1}: branch: Reset to sql_script@{1}

Expected behaviour:
- restore branch to pre-rebase location on out of memory exception
- not to fall with out of memory in the first place. But for our
repository that could be fixed only after either:
--- a) msysgit would have x64 binary (currently it's not available)
--- b) rebase -m option could be used by default somehow (currently
it's not possible so specify default -m)

--
Alexander Kostikov

Re: Rebase doesn't restore branch pointer back on out of memory

[Andrew Wong]

On 10/03/2012 03:47 PM, Alexander Kostikov wrote:
> Expected behaviour:
> - restore branch to pre-rebase location on out of memory exception
> - not to fall with out of memory in the first place. But for our
> repository that could be fixed only after either:
> --- a) msysgit would have x64 binary (currently it's not available)
> --- b) rebase -m option could be used by default somehow (currently
> it's not possible so specify default -m)
There are already some logic in "rebase" that will handles failures. And 
in the case of failures, the behavior is that "rebase" will just stop 
and not modify the branch. That allows you can go back to the pre-rebase 
state by "rebase --abort".

In your case, it's possible that "rebase" is failing at unexpected 
places, and the error wasn't caught. I tried a few simple cases by 
forcing some commands to fail during a rebase, but I couldn't reproduce 
the behavior that you're having. It might help if we can figure out 
which part of "rebase" or "git" is failing (or running out of memory).

And since you're using msysgit, I guess another possible source of the 
problem is be that msysgit is not catching the error properly, or not 
relying the error back to git properly.

Re: Rebase doesn't restore branch pointer back on out of memory

[Andrew Wong]

On 10/03/2012 06:35 PM, Alexander Kostikov wrote:
>> That allows you can go back to the pre-rebase state by
>> "rebase --abort".
> rebase --abort command were not available. I guess rebase file was not created.
I meant "rebase --abort" would be available *if* the error was caught by 
"rebase". But in your case, "rebase" is probably dying somewhere and the 
error was not caught, causing "rebase" to think that everything 
completed successfully, and go ahead to update the branch.

> Is there a way to include some log verbose mode to detect where
> exactly error happens?
There isn't any built-in to git itself. But one way to get more info is 
running the rebase command this way:
     env SHELLOPTS="verbose" git rebase <your arguments>

That should print out every shell command that rebase executes. Having 
the last page of that output should give us enough context as to where 
it's failing.

Just a wild guess: rebase is probably failing at the "format-patch" command.
It'd also be interesting to see if "rebase -i" will also workaround the 
issue. But like you said, there's no way set "-i" or "-m" as the default.

Re: Rebase doesn't restore branch pointer back on out of memory

[Alexander Kostikov]

> Having the
> last page of that output should give us enough context as to where it's
> failing.
Full script is uploaded to
https://dl.dropbox.com/u/10828740/rebase.log Here is the last page:

-----------------------------------[code]
if test -s "$dotest"/rewritten; then
    git notes copy --for-rewrite=rebase < "$dotest"/rewritten
    if test -x "$GIT_DIR"/hooks/post-rewrite; then
        "$GIT_DIR"/hooks/post-rewrite rebase < "$dotest"/rewritten
    fi
fi

rm -fr "$dotest"
git gc --auto
git rev-parse HEAD

ret=$?
test 0 != $ret -a -d "$state_dir" && write_basic_state
exit $ret
-----------------------------------[/code]


> It'd also be interesting to see if "rebase -i" will also workaround the
> issue.

rebase -i fails with different error:

» git rebase -i master rebase_debug
fatal: Out of memory, malloc failed (tried to allocate 458753 bytes)

Do you need verbose log for it as well?

-- Alexander


On Thu, Oct 4, 2012 at 8:13 AM, Andrew Wong <andrew.kw.w.lists@gmail.com> wrote:
> On 10/03/2012 06:35 PM, Alexander Kostikov wrote:
>>>
>>> That allows you can go back to the pre-rebase state by
>>> "rebase --abort".
>>
>> rebase --abort command were not available. I guess rebase file was not
>> created.
>
> I meant "rebase --abort" would be available *if* the error was caught by
> "rebase". But in your case, "rebase" is probably dying somewhere and the
> error was not caught, causing "rebase" to think that everything completed
> successfully, and go ahead to update the branch.
>
>
>> Is there a way to include some log verbose mode to detect where
>> exactly error happens?
>
> There isn't any built-in to git itself. But one way to get more info is
> running the rebase command this way:
>     env SHELLOPTS="verbose" git rebase <your arguments>
>
> That should print out every shell command that rebase executes. Having the
> last page of that output should give us enough context as to where it's
> failing.
>
> Just a wild guess: rebase is probably failing at the "format-patch" command.
> It'd also be interesting to see if "rebase -i" will also workaround the
> issue. But like you said, there's no way set "-i" or "-m" as the default.



-- 
Alexander Kostikov

Re: Rebase doesn't restore branch pointer back on out of memory

[Alexander Kostikov]

> rebase -i fails with different error:
Also in case of rebase -i the branch pointer is not changed. Thus
nothing to fix there.

-- Alexander

On Thu, Oct 4, 2012 at 2:09 PM, Alexander Kostikov
<alex.kostikov@gmail.com> wrote:
>> Having the
>> last page of that output should give us enough context as to where it's
>> failing.
> Full script is uploaded to
> https://dl.dropbox.com/u/10828740/rebase.log Here is the last page:
>
> -----------------------------------[code]
> if test -s "$dotest"/rewritten; then
>     git notes copy --for-rewrite=rebase < "$dotest"/rewritten
>     if test -x "$GIT_DIR"/hooks/post-rewrite; then
>         "$GIT_DIR"/hooks/post-rewrite rebase < "$dotest"/rewritten
>     fi
> fi
>
> rm -fr "$dotest"
> git gc --auto
> git rev-parse HEAD
>
> ret=$?
> test 0 != $ret -a -d "$state_dir" && write_basic_state
> exit $ret
> -----------------------------------[/code]
>
>
>> It'd also be interesting to see if "rebase -i" will also workaround the
>> issue.
>
> rebase -i fails with different error:
>
> » git rebase -i master rebase_debug
> fatal: Out of memory, malloc failed (tried to allocate 458753 bytes)
>
> Do you need verbose log for it as well?
>
> -- Alexander
>
>
> On Thu, Oct 4, 2012 at 8:13 AM, Andrew Wong <andrew.kw.w.lists@gmail.com> wrote:
>> On 10/03/2012 06:35 PM, Alexander Kostikov wrote:
>>>>
>>>> That allows you can go back to the pre-rebase state by
>>>> "rebase --abort".
>>>
>>> rebase --abort command were not available. I guess rebase file was not
>>> created.
>>
>> I meant "rebase --abort" would be available *if* the error was caught by
>> "rebase". But in your case, "rebase" is probably dying somewhere and the
>> error was not caught, causing "rebase" to think that everything completed
>> successfully, and go ahead to update the branch.
>>
>>
>>> Is there a way to include some log verbose mode to detect where
>>> exactly error happens?
>>
>> There isn't any built-in to git itself. But one way to get more info is
>> running the rebase command this way:
>>     env SHELLOPTS="verbose" git rebase <your arguments>
>>
>> That should print out every shell command that rebase executes. Having the
>> last page of that output should give us enough context as to where it's
>> failing.
>>
>> Just a wild guess: rebase is probably failing at the "format-patch" command.
>> It'd also be interesting to see if "rebase -i" will also workaround the
>> issue. But like you said, there's no way set "-i" or "-m" as the default.
>
>
>
> --
> Alexander Kostikov



-- 
Alexander Kostikov

Re: Rebase doesn't restore branch pointer back on out of memory

[Andrew Wong]

On 10/04/2012 05:09 PM, Alexander Kostikov wrote:
> Full script is uploaded to
> https://dl.dropbox.com/u/10828740/rebase.log  Here is the last page:
Judging from that log, I'm pretty sure "rebase" is failing at 
"format-patch". I was able to reproduce the issue you're having: 
"rebase" finished and modified the branch even though it actually failed.

"rebase" is not catching that error. I'll try to come up with a patch to 
fix it later tonight, so that "rebase" will fail correctly. And when it 
does, you'll be able to do "rebase --abort" to go back to your original 
state.

Re: Rebase doesn't restore branch pointer back on out of memory

[Alexander Kostikov]

Thanks, Andrew!
I'm looking forward for the patch.

On Thu, Oct 4, 2012 at 3:52 PM, Andrew Wong <andrew.kw.w@gmail.com> wrote:
> On 10/04/2012 05:09 PM, Alexander Kostikov wrote:
>>
>> Full script is uploaded to
>> https://dl.dropbox.com/u/10828740/rebase.log  Here is the last page:
>
> Judging from that log, I'm pretty sure "rebase" is failing at
> "format-patch". I was able to reproduce the issue you're having: "rebase"
> finished and modified the branch even though it actually failed.
>
> "rebase" is not catching that error. I'll try to come up with a patch to fix
> it later tonight, so that "rebase" will fail correctly. And when it does,
> you'll be able to do "rebase --abort" to go back to your original state.
>



-- 
Alexander Kostikov

Re: Rebase doesn't restore branch pointer back on out of memory

[Andrew Wong]

'format-patch' is failing due to out of memory, and the error not being caught.
So 'rebase' thinks 'am' has completed successfully and continue on with
cleanup. i.e. move_to_original_branch
So the user loses commits from the original head, and have to rely on reflog to
return to the original head.

Since the exit status of 'format-patch' is not available, we have to use ||
with 'format-patch' to handle the error.  Also, when 'format-patch' fails, the
state_dir does not necessarily exist, so I'm putting the 'format-patch-failed'
file inside GIT_DIR. Is there a better location to put such a file?

The way I handle the error feels a bit bruteforced.  Any suggestions on a
better way to handle the error?

I also thought about separating 'format-patch' and 'am' into two separate
commands, and use an intermediate file to store the output of 'format-patch'.
But the intermediate file could get very big, so it didn't seem like a good
idea.

Andrew Wong (1):
  rebase: Handle cases where format-patch fails

 git-rebase--am.sh | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

-- 
1.8.0.rc0.18.gf84667d

[RFC] rebase: Handle cases where format-patch fails

[Andrew Wong]

'format-patch' could fail due to reasons such as out of memory. Such
failures are not detected or handled, which causes rebase to incorrectly
think that it completed successfully and continue with cleanup. i.e.
calling move_to_original_branch

Since only the exit status of the last command in the pipeline is
available, we rely on || to detect whether 'format-patch' has failed.

Also print messages to help user with how to recover from such failures.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 git-rebase--am.sh | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/git-rebase--am.sh b/git-rebase--am.sh
index 392ebc9..8dae804 100644
--- a/git-rebase--am.sh
+++ b/git-rebase--am.sh
@@ -26,10 +26,43 @@ then
 	# makes this easy
 	git cherry-pick --allow-empty "$revisions"
 else
-	git format-patch -k --stdout --full-index --ignore-if-in-upstream \
+	( git format-patch -k --stdout --full-index --ignore-if-in-upstream \
 		--src-prefix=a/ --dst-prefix=b/ \
-		--no-renames $root_flag "$revisions" |
+		--no-renames $root_flag "$revisions" ||
+		echo $? > "$GIT_DIR"/format-patch-failed ) |
 	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg"
+	ret=$?
+	if test -f "$GIT_DIR"/format-patch-failed
+	then
+		ret=1
+		rm -f "$GIT_DIR"/format-patch-failed
+		if test -d "$state_dir"
+		then
+			echo
+			echo "'git format-patch' seems to have failed in the middle of 'git am'."
+			echo "If you continue rebasing, you will likely be losing some commits."
+			echo "It is recommended that you abort rebasing by running:"
+			echo
+			echo "    git rebase --abort"
+			echo
+		else
+			echo
+			echo "'git format-patch' seems to have failed before 'git am' started."
+			echo "It is impossible to continue or abort rebasing."
+			echo "You have to use the following to return to your original head:"
+			echo
+			case "$head_name" in
+			refs/*)
+				echo "    git checkout $head_name"
+				;;
+			*)
+				echo "    git checkout $orig_head"
+				;;
+			esac
+			echo
+		fi
+	fi
+	test 0 != $ret && false
 fi && move_to_original_branch
 
 ret=$?
-- 
1.8.0.rc0.18.gf84667d

Re: [RFC] rebase: Handle cases where format-patch fails

[Junio C Hamano]

Andrew Wong <andrew.kw.w@gmail.com> writes:

> 'format-patch' could fail due to reasons such as out of memory. Such
> failures are not detected or handled, which causes rebase to incorrectly
> think that it completed successfully and continue with cleanup. i.e.
> calling move_to_original_branch
>
> Since only the exit status of the last command in the pipeline is
> available, we rely on || to detect whether 'format-patch' has failed.
>
> Also print messages to help user with how to recover from such failures.
>
> Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
> ---
>  git-rebase--am.sh | 37 +++++++++++++++++++++++++++++++++++--
>  1 file changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/git-rebase--am.sh b/git-rebase--am.sh
> index 392ebc9..8dae804 100644
> --- a/git-rebase--am.sh
> +++ b/git-rebase--am.sh
> @@ -26,10 +26,43 @@ then
>  	# makes this easy
>  	git cherry-pick --allow-empty "$revisions"
>  else
> -	git format-patch -k --stdout --full-index --ignore-if-in-upstream \
> +	( git format-patch -k --stdout --full-index --ignore-if-in-upstream \
>  		--src-prefix=a/ --dst-prefix=b/ \
> -		--no-renames $root_flag "$revisions" |
> +		--no-renames $root_flag "$revisions" ||
> +		echo $? > "$GIT_DIR"/format-patch-failed ) |

Please make sure there is no marker-file that was leftover from
previous invocation or whatever reason, e.g.

	rm -f "$GIT_DIR/format-patch-failed"
        (
		git format-patch -k --stdout --full-index --ignore-if-in-upstream \
			--src-prefix=a/ --dst-prefix=b/ \
			--no-renames $root_flag "$revisions" ||
		echo $? >"$GIT_DIR"/format-patch-failed
	) |
  	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg"

But when format-patch dies for whatever reason, it is likely that
the partial output will cause "am" to barf on the last part of it
(either "missing patch text" if it stops in the middle of commit log
message, or "corrupt patch" if it stops in the middle of a hunk).
It may make sense to make this all-or-none, i.e. when format-patch
fails, you do not even start "am", something like...

	rm -f "$GIT_DIR/patch-input"
        if ! git format-patch -k --stdout >"$GIT_DIR/patch-input" \
	        --full-index --ignore-if-in-upstream \
		--src-prefix=a/ --dst-prefix=b/ \
		--no-renames $root_flag "$revisions"
	then
		... format-patch barfed, here is how to deal with it...
	else
        	git am <"$GIT_DIR/patch-input" $git_am_opt ...
	fi
	rm -f "$GIT_DIR/patch-input"

but I wonder what the performance implication would be for normal cases.

> +	ret=$?
> +	if test -f "$GIT_DIR"/format-patch-failed
> +	then
> +		ret=1
> +		rm -f "$GIT_DIR"/format-patch-failed
> +		if test -d "$state_dir"
> +		then
> +			echo
> +			echo "'git format-patch' seems to have failed in the middle of 'git am'."
> +			echo "If you continue rebasing, you will likely be losing some commits."
> +			echo "It is recommended that you abort rebasing by running:"
> +			echo
> +			echo "    git rebase --abort"
> +			echo
> +		else
> +			echo
> +			echo "'git format-patch' seems to have failed before 'git am' started."
> +			echo "It is impossible to continue or abort rebasing."
> +			echo "You have to use the following to return to your original head:"
> +			echo
> +			case "$head_name" in
> +			refs/*)
> +				echo "    git checkout $head_name"
> +				;;
> +			*)
> +				echo "    git checkout $orig_head"
> +				;;
> +			esac
> +			echo
> +		fi
> +	fi
> +	test 0 != $ret && false
>  fi && move_to_original_branch
>  
>  ret=$?

Re: [RFC] rebase: Handle cases where format-patch fails

[Andrew Wong]

Here's an alternate method for handling 'format-patch' failing.  We remove the
pipe between 'format-patch' and 'am' by storing the patch in an intermediate
file. This means we can gurantee that 'am' is always invokved with the complete
input.

I did some timing on rebasing 500 commits from the git repo.  The patch file
had a size of 6.9MB, but the overall timings between the pipe approach and
intermediate file approach are approximately the same.  I did the tests on a
Linux machine, so I don't know what the impact would be on other platforms, or
in repos with larger files and perhaps binary files.

Andrew Wong (1):
  rebase: Handle cases where format-patch fails

 git-rebase--am.sh | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

-- 
1.8.0.rc0.19.ga19ab82.dirty

[RFC] rebase: Handle cases where format-patch fails

[Andrew Wong]

'format-patch' could fail due to reasons such as out of memory. Such
failures are not detected or handled, which causes rebase to incorrectly
think that it completed successfully and continue with cleanup. i.e.
calling move_to_original_branch

Instead of using a pipe, we separate 'format-patch' and 'am' by using an
intermediate file. This gurantees that we can invoke 'am' with the
complete input, or not invoking 'am' at all if 'format-patch' failed.

Also print messages to help user with how to recover from such failures.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 git-rebase--am.sh | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/git-rebase--am.sh b/git-rebase--am.sh
index 392ebc9..a955b38 100644
--- a/git-rebase--am.sh
+++ b/git-rebase--am.sh
@@ -26,10 +26,32 @@ then
 	# makes this easy
 	git cherry-pick --allow-empty "$revisions"
 else
-	git format-patch -k --stdout --full-index --ignore-if-in-upstream \
+	rm -f "$GIT_DIR/format-patch"
+	if ! git format-patch -k --stdout --full-index --ignore-if-in-upstream \
 		--src-prefix=a/ --dst-prefix=b/ \
-		--no-renames $root_flag "$revisions" |
-	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg"
+		--no-renames $root_flag "$revisions" > "$GIT_DIR/format-patch" && ret=$?
+	then
+		rm "$GIT_DIR/format-patch"
+		echo
+		echo "'git format-patch' seems to have failed."
+		echo "It is impossible to continue or abort rebasing."
+		echo "You have to use the following to return to your original head:"
+		echo
+		case "$head_name" in
+		refs/*)
+			echo "    git checkout $head_name"
+			;;
+		*)
+			echo "    git checkout $orig_head"
+			;;
+		esac
+		echo
+		exit $ret
+	fi
+
+	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg" < "$GIT_DIR/format-patch" || ret=$?
+	rm -f "$GIT_DIR/format-patch"
+	test 0 != ret && ( exit $ret )
 fi && move_to_original_branch
 
 ret=$?
-- 
1.8.0.rc0.19.ga19ab82.dirty

Re: [RFC] rebase: Handle cases where format-patch fails

[Junio C Hamano]

Andrew Wong <andrew.kw.w@gmail.com> writes:

> 'format-patch' could fail due to reasons such as out of memory. Such
> failures are not detected or handled, which causes rebase to incorrectly
> think that it completed successfully and continue with cleanup. i.e.
> calling move_to_original_branch
>
> Instead of using a pipe, we separate 'format-patch' and 'am' by using an
> intermediate file. This gurantees that we can invoke 'am' with the
> complete input, or not invoking 'am' at all if 'format-patch' failed.
>
> Also print messages to help user with how to recover from such failures.
>
> Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
> ---
>  git-rebase--am.sh | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/git-rebase--am.sh b/git-rebase--am.sh
> index 392ebc9..a955b38 100644
> --- a/git-rebase--am.sh
> +++ b/git-rebase--am.sh
> @@ -26,10 +26,32 @@ then
>  	# makes this easy
>  	git cherry-pick --allow-empty "$revisions"
>  else
> -	git format-patch -k --stdout --full-index --ignore-if-in-upstream \
> +	rm -f "$GIT_DIR/format-patch"
> +	if ! git format-patch -k --stdout --full-index --ignore-if-in-upstream \
>  		--src-prefix=a/ --dst-prefix=b/ \
> -		--no-renames $root_flag "$revisions" |
> -	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg"
> +		--no-renames $root_flag "$revisions" > "$GIT_DIR/format-patch" && ret=$?
> +	then

Is it just me?  I find this construct

	if ! cmd && ret=$?
        then

very hard to wrap my mind around.  Why not

	git format-patch ... just as before ... \
          ... >"$GIT_DIR/formatted-patches" || {
		# error handling or advices come here...
                rm -f "$GIT_DIR/formatted-patches"
		exit 1
	}

	git am ... just as before ... "$GIT_DIR/formatted-patches" || {
		# possibly another error handling or advices come here...
		rm -f "$GIT_DIR/formatted-patches"
		exit 1
	}

without changing anything else?

> +		rm "$GIT_DIR/format-patch"
> +		echo
> +		echo "'git format-patch' seems to have failed."
> +		echo "It is impossible to continue or abort rebasing."
> +		echo "You have to use the following to return to your original head:"
> +		echo
> +		case "$head_name" in
> +		refs/*)
> +			echo "    git checkout $head_name"
> +			;;
> +		*)
> +			echo "    git checkout $orig_head"
> +			;;
> +		esac

You _know_ format-patch failed, not just "seems to have", at this
point, no?  Why is it impossible to abort?

What have we done before reaching to this point?  We know we are
doing the basic "git rebase", without any funny "-m/-i/-p" business,
so the only thing we have done are (1) detached HEAD at the new
onto, (2) set ORIG_HEAD to point at the original tip of the branch
being rebased (or the commit we were sitting at, if we are rebasing
a detached history), and (3) head_name has the refname of the
original branch (or detached HEAD) and branch_name has the name of
the branch (or HEAD).

Shouldn't we be just rewinding what we have done so far and error
the whole thing out instead?  Perhaps the first "# error handling or
advises come here..." part may simply be

	case "$head_name" in
	refs/heads/*)
		git checkout "$head_name"
                ;;
	*)
		git checkout "$orig_head"
                ;;
	esac
	cat >&2 <<-\EOF
	Error was found while preparing the patches ($revisions) to
        replay on the rewound head. You cannot rebase this history.
        EOF

or something like that.  The format-patch output (and its error) may
be of interest in getting help going forward.

Re: Rebase doesn't restore branch pointer back on out of memory

[Andrew Wong]

For the 'format-patch' part, originally I was going to do something like:

	git format-patch ... || {
		...
	}

But later I thought it's better to use a consistent style as the following
'am' part.

For the 'am' part, if we kept the following line at the end of the if-block:

	fi && move_to_original_branch

then, before exiting the if-block, we would have to do something like:

	test 0 != $ret && false

which seems a bit ugly to me. So I removed the use of '&&', and rearrange the
'write_basic_state' and 'move_to_original_branch' to make the logic flow a bit
better and easier to read.

Andrew Wong (1):
  rebase: Handle cases where format-patch fails

 git-rebase--am.sh | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

-- 
1.8.0.rc0.19.gc58a63a.dirty

[PATCH] rebase: Handle cases where format-patch fails

[Andrew Wong]

'format-patch' could fail due to reasons such as out of memory. Such
failures are not detected or handled, which causes rebase to incorrectly
think that it completed successfully and continue with cleanup. i.e.
calling move_to_original_branch

Instead of using a pipe, we separate 'format-patch' and 'am' by using an
intermediate file. This gurantees that we can invoke 'am' with the
complete input, or not invoking 'am' at all if 'format-patch' failed.

Also remove the use of '&&' at the end of the if-block, and rearrange
the 'write_basic_state' and 'move_to_original_branch' to make the logic
flow a bit better and easier to read.

Signed-off-by: Andrew Wong <andrew.kw.w@gmail.com>
---
 git-rebase--am.sh | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/git-rebase--am.sh b/git-rebase--am.sh
index 392ebc9..85b594e 100644
--- a/git-rebase--am.sh
+++ b/git-rebase--am.sh
@@ -18,6 +18,7 @@ esac
 
 test -n "$rebase_root" && root_flag=--root
 
+ret=0
 if test -n "$keep_empty"
 then
 	# we have to do this the hard way.  git format-patch completely squashes
@@ -25,13 +26,51 @@ then
 	# itself well to recording empty patches.  fortunately, cherry-pick
 	# makes this easy
 	git cherry-pick --allow-empty "$revisions"
+	ret=$?
 else
+	rm -f "$GIT_DIR/format-patch"
+
 	git format-patch -k --stdout --full-index --ignore-if-in-upstream \
 		--src-prefix=a/ --dst-prefix=b/ \
-		--no-renames $root_flag "$revisions" |
-	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg"
-fi && move_to_original_branch
+		--no-renames $root_flag "$revisions" > "$GIT_DIR/format-patch"
+	ret=$?
+
+	if test 0 != $ret
+	then
+		rm -f "$GIT_DIR/format-patch"
+
+		case "$head_name" in
+		refs/heads/*)
+			git checkout -q "$head_name"
+			;;
+		*)
+			git checkout -q "$orig_head"
+			;;
+		esac
+
+		cat >&2 <<-EOF
+
+		git encountered an error while preparing the patches to replay
+		these revisions:
+
+		    $revisions
+
+		As a result, git cannot rebase these revisions.
+		EOF
+
+		exit $?
+	fi
+
+	git am $git_am_opt --rebasing --resolvemsg="$resolvemsg" < "$GIT_DIR/format-patch"
+	ret=$?
+
+	rm -f "$GIT_DIR/format-patch"
+fi
+
+if test 0 != $ret
+then
+	test -d "$state_dir" && write_basic_state
+	exit $ret
+fi
 
-ret=$?
-test 0 != $ret -a -d "$state_dir" && write_basic_state
-exit $ret
+move_to_original_branch
-- 
1.8.0.rc0.19.gc58a63a.dirty

Re: Rebase doesn't restore branch pointer back on out of memory

[Alexander Kostikov]

Sorry to bother but I was wondering what would be the release version
that would have this patch.

-- Alexander


On Wed, Oct 10, 2012 at 8:54 PM, Andrew Wong <andrew.kw.w@gmail.com> wrote:
>
> For the 'format-patch' part, originally I was going to do something like:
>
>         git format-patch ... || {
>                 ...
>         }
>
> But later I thought it's better to use a consistent style as the following
> 'am' part.
>
> For the 'am' part, if we kept the following line at the end of the if-block:
>
>         fi && move_to_original_branch
>
> then, before exiting the if-block, we would have to do something like:
>
>         test 0 != $ret && false
>
> which seems a bit ugly to me. So I removed the use of '&&', and rearrange the
> 'write_basic_state' and 'move_to_original_branch' to make the logic flow a bit
> better and easier to read.
>
> Andrew Wong (1):
>   rebase: Handle cases where format-patch fails
>
>  git-rebase--am.sh | 51 +++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 45 insertions(+), 6 deletions(-)
>
> --
> 1.8.0.rc0.19.gc58a63a.dirty
>



--
Alexander Kostikov

Re: Rebase doesn't restore branch pointer back on out of memory

[Junio C Hamano]

Alexander Kostikov <alex.kostikov@gmail.com> writes:

> Sorry to bother but I was wondering what would be the release version
> that would have this patch.

That depends on how well the people who are interested in this
change test it to smoke out potential issues (if any) in it.

It currently is on the 'pu' branch.