[PATCH] branch: implement shortcut to delete last branch

[PATCH] branch: implement shortcut to delete last branch

[Aaron Greenberg]

This patch gives git-branch the ability to delete the previous
checked-out branch using the "-" shortcut. This shortcut already exists
for git-checkout, git-merge, and git-revert. One of my common workflows
is to do some work on a local topic branch and push it to a remote,
where it gets merged in to 'master'. Then, I switch back to my local
master, fetch the remote master, and delete the previous topic branch.

$ git checkout -b topic-a
$ # Do some work...
$ git commit -am "Implement feature A"
$ git push origin topic-a

# 'origin/topic-a' gets merged into 'origin/master'

$ git checkout master
$ git branch -d topic-a
$ # With this patch, a user could simply type
$ git branch -d -

I think it's a useful shortcut for cleaning up a just-merged branch
(or a just switched-from branch.)

[PATCH] branch: implement shortcut to delete last branch

[Aaron Greenberg]

Add support for using the "-" shortcut to delete the last checked-out
branch. This functionality already exists for git-merge, git-checkout,
and git-revert.

Signed-off-by: Aaron Greenberg <p@aaronjgreenberg.com>
---
 builtin/branch.c  | 3 +++
 t/t3200-branch.sh | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/builtin/branch.c b/builtin/branch.c
index 6d0cea9..9e37078 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -221,6 +221,9 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		char *target = NULL;
 		int flags = 0;
 
+		if (!strcmp(argv[i], "-"))
+			argv[i] = "@{-1}";
+
 		strbuf_branchname(&bname, argv[i], allowed_interpret);
 		free(name);
 		name = mkpathdup(fmt, bname.buf);
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 6c0b7ea..a3ffd54 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -776,6 +776,15 @@ test_expect_success 'deleting currently checked out branch fails' '
 	test_must_fail git branch -d my7
 '
 
+test_expect_success 'test deleting last branch' '
+	git checkout -b my7.2 &&
+	git checkout  - &&
+	sha1=$(git rev-parse my7 | cut -c 1-7) &&
+	echo "Deleted branch my7.2 (was $sha1)." >expect &&
+	git branch -d - >actual 2>&1 &&
+	test_i18ncmp expect actual
+'
+
 test_expect_success 'test --track without .fetch entries' '
 	git branch --track my8 &&
 	test "$(git config branch.my8.remote)" &&
-- 
2.7.4

Re: [PATCH] branch: implement shortcut to delete last branch

[Jeff King]

On Fri, Mar 23, 2018 at 02:09:25AM +0000, Aaron Greenberg wrote:

> This patch gives git-branch the ability to delete the previous
> checked-out branch using the "-" shortcut. This shortcut already exists
> for git-checkout, git-merge, and git-revert. One of my common workflows
> is to do some work on a local topic branch and push it to a remote,
> where it gets merged in to 'master'. Then, I switch back to my local
> master, fetch the remote master, and delete the previous topic branch.
> 
> $ git checkout -b topic-a
> $ # Do some work...
> $ git commit -am "Implement feature A"
> $ git push origin topic-a
> 
> # 'origin/topic-a' gets merged into 'origin/master'
> 
> $ git checkout master
> $ git branch -d topic-a
> $ # With this patch, a user could simply type
> $ git branch -d -
> 
> I think it's a useful shortcut for cleaning up a just-merged branch
> (or a just switched-from branch.)

I don't use "-" myself, but I can see how this would be useful. Do note
that in a discussion last year there was some hesitation about allowing
"-" for destructive commands:

  https://public-inbox.org/git/vpqh944eof7.fsf@anie.imag.fr/

I don't really have a strong opinion either way.

The details in this cover letter probably should go into the commit
message. The diff itself looks OK (the assumption of a 7-char
abbreviation in the test is a little gross, but I see you're just
following existing convention in the file).

-Peff

Re: [PATCH] branch: implement shortcut to delete last branch

[Jeff King]

[resending; I cc'd Matthieu on his address from that old thread, but it
 bounced]

On Fri, Mar 23, 2018 at 04:56:36AM -0400, Jeff King wrote:

> On Fri, Mar 23, 2018 at 02:09:25AM +0000, Aaron Greenberg wrote:
> 
> > This patch gives git-branch the ability to delete the previous
> > checked-out branch using the "-" shortcut. This shortcut already exists
> > for git-checkout, git-merge, and git-revert. One of my common workflows
> > is to do some work on a local topic branch and push it to a remote,
> > where it gets merged in to 'master'. Then, I switch back to my local
> > master, fetch the remote master, and delete the previous topic branch.
> > 
> > $ git checkout -b topic-a
> > $ # Do some work...
> > $ git commit -am "Implement feature A"
> > $ git push origin topic-a
> > 
> > # 'origin/topic-a' gets merged into 'origin/master'
> > 
> > $ git checkout master
> > $ git branch -d topic-a
> > $ # With this patch, a user could simply type
> > $ git branch -d -
> > 
> > I think it's a useful shortcut for cleaning up a just-merged branch
> > (or a just switched-from branch.)
> 
> I don't use "-" myself, but I can see how this would be useful. Do note
> that in a discussion last year there was some hesitation about allowing
> "-" for destructive commands:
> 
>   https://public-inbox.org/git/vpqh944eof7.fsf@anie.imag.fr/
> 
> I don't really have a strong opinion either way.
> 
> The details in this cover letter probably should go into the commit
> message. The diff itself looks OK (the assumption of a 7-char
> abbreviation in the test is a little gross, but I see you're just
> following existing convention in the file).
> 
> -Peff

[PATCH v2] branch: implement shortcut to delete last branch

[Aaron Greenberg]

I updated the commit message to include my first email's cover letter
and cleaned up the test.

Copying Junio, since he also had good comments in the conversation you
linked.

I can appreciate Matthieu's points on the use of "-" in destructive
commands. As of this writing, git-merge supports the "-" shorthand,
which while not destructive, is at least _mutative_. Also,
"git branch -d" is not destructive in the same way that "rm -rf" is
destructive since you can recover the branch using the reflog.

One thing to consider is that approval of this patch extends the
implementation of the "-" shorthand in a piecemeal, rather than
consistent, way (implementing it in a consistent way was the goal of
the patch set you mentioned in your previous email.) Is that okay? Or
is it better to pick up the consistent approach where it was left?

[PATCH] branch: implement shortcut to delete last branch

[Aaron Greenberg]

This patch gives git-branch the ability to delete the previous
checked-out branch using the "-" shortcut. This shortcut already exists
for git-checkout, git-merge, and git-revert. A common workflow is

1. Do some work on a local topic-branch and push it to a remote.
2. 'remote/topic-branch' gets merged in to 'remote/master'.
3. Switch back to local master and fetch 'remote/master'.
4. Delete previously checked-out local topic-branch.

$ git checkout -b topic-a
$ # Do some work...
$ git commit -am "Implement feature A"
$ git push origin topic-a

$ git checkout master
$ git branch -d topic-a
$ # With this patch, a user could simply type
$ git branch -d -

"-" is a useful shortcut for cleaning up a just-merged branch
(or a just switched-from branch.)

Signed-off-by: Aaron Greenberg <p@aaronjgreenberg.com>
---
 builtin/branch.c  | 3 +++
 t/t3200-branch.sh | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/builtin/branch.c b/builtin/branch.c
index 6d0cea9..9e37078 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -221,6 +221,9 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		char *target = NULL;
 		int flags = 0;
 
+		if (!strcmp(argv[i], "-"))
+			argv[i] = "@{-1}";
+
 		strbuf_branchname(&bname, argv[i], allowed_interpret);
 		free(name);
 		name = mkpathdup(fmt, bname.buf);
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 6c0b7ea..78c25aa 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -776,6 +776,14 @@ test_expect_success 'deleting currently checked out branch fails' '
 	test_must_fail git branch -d my7
 '
 
+test_expect_success 'test deleting last branch' '
+	git checkout -b my7.1 &&
+	git checkout  - &&
+	test_path_is_file .git/refs/heads/my7.1 &&
+	git branch -d - &&
+	test_path_is_missing .git/refs/heads/my7.1
+'
+
 test_expect_success 'test --track without .fetch entries' '
 	git branch --track my8 &&
 	test "$(git config branch.my8.remote)" &&
-- 
2.7.4

Re: [PATCH v2] branch: implement shortcut to delete last branch

[Jeff King]

On Fri, Mar 23, 2018 at 10:40:34PM +0000, Aaron Greenberg wrote:

> I updated the commit message to include my first email's cover letter
> and cleaned up the test.

Thanks. This one looks good to me.

> I can appreciate Matthieu's points on the use of "-" in destructive
> commands. As of this writing, git-merge supports the "-" shorthand,
> which while not destructive, is at least _mutative_. Also,
> "git branch -d" is not destructive in the same way that "rm -rf" is
> destructive since you can recover the branch using the reflog.

There's a slight subtlety there with the reflog, because "branch -d"
actually _does_ delete the reflog for the branch. By definition if
you've found the branch with "-" then it was just checked out, so you at
least have the old tip. But the branch's whole reflog is gone for good.

That said, I'd still be OK with it.

> One thing to consider is that approval of this patch extends the
> implementation of the "-" shorthand in a piecemeal, rather than
> consistent, way (implementing it in a consistent way was the goal of
> the patch set you mentioned in your previous email.) Is that okay? Or
> is it better to pick up the consistent approach where it was left?

I don't have a real opinion on whether it should be implemented
everywhere or not. But IMHO it's OK to do it piecemeal for now either
way, unless we're really sure it's time to move to respecting it
everywhere. Because we can always convert a
piecemeal-but-covers-everything state to centralized parsing as a
cleanup.

-Peff

Re: [PATCH v2] branch: implement shortcut to delete last branch

[git]

Thanks for Cc-ing me, and sorry for not being very responsive these
days :-\.

Jeff King writes:

> On Fri, Mar 23, 2018 at 10:40:34PM +0000, Aaron Greenberg wrote:
>
>> I can appreciate Matthieu's points on the use of "-" in destructive
>> commands. As of this writing, git-merge supports the "-" shorthand,
>> which while not destructive, is at least _mutative_. Also,
>> "git branch -d" is not destructive in the same way that "rm -rf" is
>> destructive since you can recover the branch using the reflog.
>
> There's a slight subtlety there with the reflog, because "branch -d"
> actually _does_ delete the reflog for the branch. By definition if
> you've found the branch with "-" then it was just checked out, so you at
> least have the old tip. But the branch's whole reflog is gone for good.
>
> That said, I'd still be OK with it.

I don't have objection either.

Anyway, we're supporting this "-" shortcut in more and more commands
(partly because it's a nice microproject, but it probably makes sense),
so the "consistency" argument becomes more and more important, and is
probably more important than the (relative) safety of not having the
shortcut.

>> One thing to consider is that approval of this patch extends the
>> implementation of the "-" shorthand in a piecemeal, rather than
>> consistent, way (implementing it in a consistent way was the goal of
>> the patch set you mentioned in your previous email.) Is that okay? Or
>> is it better to pick up the consistent approach where it was left?
>
> I don't have a real opinion on whether it should be implemented
> everywhere or not. But IMHO it's OK to do it piecemeal for now either
> way, unless we're really sure it's time to move to respecting it
> everywhere. Because we can always convert a
> piecemeal-but-covers-everything state to centralized parsing as a
> cleanup.

Not sure whether it's already been mentionned here, but a previous
attempt is here:

  https://public-inbox.org/git/1488007487-12965-1-git-send-email-kannan.siddharth12@gmail.com/

My understanding is that the actual code is quite straightforward, but
1) it needs a few cleanup patches to be done correctly, and 2) there are
corner-cases to deal with like avoiding a commit message like "merge
branch '-' into 'foo'". Regarding 2), any piecemeal implementation with
proper tests is a step in the right direction.

--
Matthieu Moy
https://matthieu-moy.fr/

Re: [PATCH v2] branch: implement shortcut to delete last branch

[Junio C Hamano]

git@matthieu-moy.fr writes:

>> That said, I'd still be OK with it.
>
> I don't have objection either.

FWIW, I do not even buy the "destructive commands should force
spelling things out even more" argument in the first place.

    $ git checkout somelongtopicname
    $ work work work
    $ git checkout master && git merge -
    $ git branch -d -

would be a lot less error-prone than the user being forced to write
last step in longhand

    $ git branch -d someotherlongtopicname

and destroying an unrelated but similarly named branch.

So obviously I am OK with it, too.

As long as we do not regress end-user experience, that is.  For
example, "git merge @{-1}" in the above sequence would record the
fact that the resulting commit is a merge of 'somelongtopicname',
not literally "@{-1}", in its log message.  It would be a sad
regression if it suddenly starts to say "Merge branch '-'" [*1*],
for example.


[Reference]

*1* https://public-inbox.org/git/xmqqinnsegxb.fsf@gitster.mtv.corp.google.com/