Re: [PATCH] branch -l: print useful info whilst rebasing a non-local branch

From: Jeff King <peff@peff.net>
Date: Mar 25, 2018, 04:10 UTC
Message-ID: <20180325041056.GA22321@sigill.intra.peff.net>
In-Reply-To: <87ea8cac-c745-b7e6-7804-5116cd94ed48@gmail.com>

On Sun, Mar 25, 2018 at 09:11:34AM +0530, Kaartic Sivaraam wrote:

Show 8 quoted lines

> >> When rebasing interacitvely (rebase -i), "git branch -l" prints a line
> > 
> > The "git branch -l" threw me since "-l" is short for --create-reflog.
> > I'm guessing you meant "git branch --list".
> 
> That's surprising, I just tried "git branch -l" on a repository and I
> did get a list of branch names. Is this a consequence of some option
> parsing weirdness ?!

Sort of. The "-l" option causes us to set the "reflog" variable to 1. And then we have no other command-line options, so we default to "--list" mode. The listing code does not look at the "reflog" variable at all, so it's just silently ignored.

So:

  git branch -l

_looks_ like it works, but only because list mode is the default. If you did:

  git branch -l foo

you would find that it does list "foo" at all, but instead creates a new branch "foo" with reflog.

Show 5 quoted lines

> To be honest, I actually assumed "-l" to be a shorthand for "--list" and
> didn't check with it in the documentation; which I should have. Sorry,
> for that. I still wonder why "git branch -l" prints a list of branch
> names when it is not a shorthand for "--list" ? (BTW, I'm also surprised
> by the fact that "-l" is not act shorthand for "--list"!)

It's historical and quite unfortunate. Doubly so since probably nobody has ever actually wanted to use the short "-l" to create a reflog, since it's typically the default and has been for a decade.

We've been hesitant to change it due to backwards compatibility. While "branch" is generally considered porcelain, it probably is the main scripting interface for creating branches (the only other option would be using "update-ref" manually). So I dunno. Maybe it would be OK to transition.

Alternatively, we could at least detect the situation that confused you:

diff --git a/builtin/branch.c b/builtin/branch.c
index 6d0cea9d4b..89e7fdc89c 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -676,6 +676,9 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		colopts = 0;
 	}
 
+	if (list && reflog)
+		die(_("--reflog in list mode does not make sense"));
+
 	if (force) {
 		delete *= 2;
 		rename *= 2;

That doesn't help somebody mistakenly doing "git branch -l foo", but
more likely they'd do "git branch -l jk/*" if they were trying to list
branches (and then "branch" would barf with "that's not a valid branch
name", though that may still leave them quite confused).

-Peff