Re: [PATCH v2] git-rebase: Teach rebase "-" shorthand.

Brian Gesiak [off-list ref] writes:

A handful of issues here:

 * "1>target" looks unconventional and wastes readers' time, forcing
   them to wonder if there is anything special going on, only to
   realize there isn't anything noteworthy.  Saying ">target" like
   everybody else does avoids attracting unnecessary attention.

 * "rebase using shorthand" is somewhat a myopic title; it assumes
   that the only short-hand relevant to rebase will be that a "-"
   stands for "@{-1}" to specify the branch we rebase the current
   branch off of.

 * The usual filename for the output from the command being tested
   is 'actual', and the usual filename for the expected output is
   'expect'.  In this case, you are verifying that the output from
   "rebase -" is the same as the output from "rebase @{-1}", so it
   is more conventional to call the former 'actual' and the latter
   'expect'.

 * Is the eye-candy output to the standard output what is the most
   interesting during the execution of a rebase?  Wouldn't we be
   more interested to make sure that we did transplant the history
   on the same commit between two cases?

   "rebase -" with your change still says something like this:

        First, rewinding head to replay your work on top of it...
        Fast-forwarded HEAD to @{-1}.

   instead of "Fast-forwarded HEAD to -".  Somebody may later want
   to "fix" this, making these two eye-candy output to be different
   from each other, and what your test expects will no longer hold
   (not that I think it is better to say "-" instead of @{-1}
   there).


I'll tentatively queue it with a minor tweak (see below).

Thanks.

-- >8 --
From: Brian Gesiak <redacted>
Date: Wed, 19 Mar 2014 20:02:15 +0900
Subject: [PATCH] rebase: allow "-" short-hand for the previous branch

Teach rebase the same shorthand as checkout and merge to name the
branch to rebase the current branch on; that is, that "-" means "the
branch we were previously on".

Requested-by: Tim Chase [off-list ref]
Signed-off-by: Brian Gesiak <redacted>
Signed-off-by: Junio C Hamano <redacted>
---
 git-rebase.sh     |  4 ++++
 t/t3400-rebase.sh | 17 +++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/git-rebase.sh b/git-rebase.sh
index 8a3efa2..658c003 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh

@@ -449,6 +449,10 @@ then
 		test "$fork_point" = auto && fork_point=t
 		;;
 	*)	upstream_name="$1"
+		if test "$upstream_name" = "-"
+		then
+			upstream_name="@{-1}"
+		fi
 		shift
 		;;
 	esac

diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index 6d94b1f..80e0a95 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh

@@ -88,6 +88,23 @@ test_expect_success 'rebase from ambiguous branch name' '
 	git rebase master
 '
 
+test_expect_success 'rebase off of the previous branch using "-"' '
+	git checkout master &&
+	git checkout HEAD^ &&
+	git rebase @{-1} >expect.messages &&
+	git merge-base master HEAD >expect.forkpoint &&
+
+	git checkout master &&
+	git checkout HEAD^ &&
+	git rebase - >actual.messages &&
+	git merge-base master HEAD >actual.forkpoint &&
+
+	test_cmp expect.forkpoint actual.forkpoint &&
+	# the next one is dubious---we may want to say "-",
+	# instead of @{-1}, in the message
+	test_i18ncmp expect.messages actual.messages
+'
+
 test_expect_success 'rebase a single mode change' '
 	git checkout master &&
 	git branch -D topic &&

-- 
1.9.1-423-g4596e3a

On Wed, Mar 19, 2014 at 10:53:01AM -0700, Junio C Hamano wrote:

   "rebase -" with your change still says something like this:

        First, rewinding head to replay your work on top of it...
        Fast-forwarded HEAD to @{-1}.

   instead of "Fast-forwarded HEAD to -".  Somebody may later want
   to "fix" this, making these two eye-candy output to be different
   from each other, and what your test expects will no longer hold
   (not that I think it is better to say "-" instead of @{-1}
   there).

I don't think either of these is correct.  When using "-" with the
commands that already support it, I have occasionally found that "-"
isn't what I thought it was.

Can we use `git name-rev` to put the actual name here, so that people
who have not done what they intended can hopefully notice sooner?

Thank you for the feedback and tweaks!

Is the eye-candy output to the standard output what is the most
interesting during the execution of a rebase?  Wouldn't we be
more interested to make sure that we did transplant the history
on the same commit between two cases?

I agree. I'll consult the other tests to see how to write such a test.

Can we use `git name-rev` to put the actual name here, so that people
who have not done what they intended can hopefully notice sooner?

This sounds like a great idea! Doing so would mirror how `git checkout`
behaves; checkout informs the user of which branch they have switched
to when using the "-" shorthand: "Switched to branch 'master'".

Should I submit a new patch, or reroll this one?

- Brian Gesiak