Re: [PATCH 1/1] builtin/pull.c: use config value of autostash

From: Philippe Blain <levraiphilippeblain@gmail.com>
Date: Jan 14, 2022, 03:14 UTC
Message-ID: <8d19623b-4b11-8ecc-8f27-17ad4ba4167a@gmail.com>
In-Reply-To: <xmqqee5bfaof.fsf@gitster.g>

Hi Junio,

Le 2022-01-13 à 19:00, Junio C Hamano a écrit :

Show 8 quoted lines

> Junio C Hamano <gitster@pobox.com> writes:
> 
>> Here is how I would explain your change.
> 
> This topic is in "Expecting an ack or two" state for some time.
> 
>   - Philippe, are you OK with the attached patch?  If so throw your
>     Signed-off-by to this thread.

I'm not 100% OK since as I remarked to John in [1], I don't think all 4 tests are necessary, 3 out of 4 are duplicates of existing tests, and I would have put the new test in t5520 with 'git pull's other "autostash" tests. I hoped that John would incorporate my suggestions in a v2, but he seems to be busy, so I'm including an updated patch at the end of this email. I only slightly edited the commit message you wrote, so thanks for that. 'pb/pull-rebase-autostash-fix' could be replaced by the patch below, I would think.

Show 5 quoted lines

>   - John, if you find Philippe's implementation a good idea (I think
>     it is, as it is simpler and cleaner) after reading and
>     understanding it, please throw an Acked-by or Reviewed-by to this
>     thread.
>

Thanks,

Philippe.

[1] https://lore.kernel.org/git/fe0b7337-3005-d09c-a3b6-65a100799676@gmail.com/

----- >8 --------- >8 --------- >8 --------- >8 --------- >8 -----
 From 28edde4e302e14c900e314268e4eeaeadc240bcb Mon Sep 17 00:00:00 2001
From: Philippe Blain <levraiphilippeblain@gmail.com>
Date: Thu, 13 Jan 2022 21:58:05 -0500
Subject: [PATCH] pull --rebase: honor rebase.autostash when fast-forwarding

"pull --rebase" internally uses the merge machinery when the other history is a descendant of ours (i.e. perform fast-forward). This came from [1], where the discussion was started from a feature request to do so. It is a bit hard to read the rationale behind it in the discussion, but it seems that it was an established fact for everybody involved that does not even need to be mentioned that fast-forwarding done with "rebase" was much undesirable than done with "merge", and more importantly, the result left by "merge" is as good as (or better than) that by "rebase".

Except for one thing. Because "git merge" does not (and should not) honor rebase.autostash, "git pull" needs to read it and forward it when we use "git merge" as a (hopefully better) substitute for "git rebase" during the fast-forwarding. But we forgot to do so (we only add "--[no-]autostash" to the "git merge" command when "git pull" itself was invoked with "--[no-]autostash" command line option.

Make sure "git merge" is run with "--autostash" when rebase.autostash is set and used to fast-forward the history on behalf of "git rebase". Incidentally this change also takes care of the case where

  - "git pull --rebase" (without other command line options) is run
  - "rebase.autostash" is not set
  - The history fast-forwards

In such a case, "git merge" is run with an explicit "--no-autostash" to prevent it from honoring merge.autostash configuration, which is what we want. After all, we want the "git merge" to pretend as if it is "git rebase" while being used for this purpose.

[1] https://lore.kernel.org/git/xmqqa8cfbkeq.fsf_-_@gitster.mtv.corp.google.com/

Reported-by: Tilman Vogel <tilman.vogel@web.de>
Co-authored-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
---
  builtin/pull.c  |  7 +++----
  t/t5520-pull.sh | 13 +++++++++++++
  2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/builtin/pull.c b/builtin/pull.c
index 1cfaf9f343..9f8a8dd716 100644
--- a/builtin/pull.c
+++ b/builtin/pull.c
@@ -1036,14 +1036,13 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
  		oidclr(&orig_head);
  
  	if (opt_rebase) {
-		int autostash = config_autostash;
-		if (opt_autostash != -1)
-			autostash = opt_autostash;
+		if (opt_autostash == -1)
+			opt_autostash = config_autostash;
  
  		if (is_null_oid(&orig_head) && !is_cache_unborn())
  			die(_("Updating an unborn branch with changes added to the index."));
  
-		if (!autostash)
+		if (!opt_autostash)
  			require_clean_work_tree(the_repository,
  				N_("pull with rebase"),
  				_("please commit or stash them."), 1, 0);
diff --git a/t/t5520-pull.sh b/t/t5520-pull.sh
index 93ecfcdd24..3e784f18a6 100755
--- a/t/t5520-pull.sh
+++ b/t/t5520-pull.sh
@@ -330,6 +330,19 @@ test_expect_success '--rebase --autostash fast forward' '
  	test_cmp_rev HEAD to-rebase-ff
  '
  
+test_expect_success '--rebase with rebase.autostash succeeds on ff' '
+	test_when_finished "rm -fr src dst actual" &&
+	git init src &&
+	test_commit -C src "initial" file "content" &&
+	git clone src dst &&
+	test_commit -C src --printf "more_content" file "more content\ncontent\n" &&
+	echo "dirty" >>dst/file &&
+	test_config -C dst rebase.autostash true &&
+	git -C dst pull --rebase  >actual 2>&1 &&
+	grep -q "Fast-forward" actual &&
+	grep -q "Applied autostash." actual
+'
+
  test_expect_success '--rebase with conflicts shows advice' '
  	test_when_finished "git rebase --abort; git checkout -f to-rebase" &&
  	git checkout -b seq &&

base-commit: e9d7761bb94f20acc98824275e317fa82436c25d
prerequisite-patch-id: 3c6b4be75d7a634bf45f0264b3f04216818a0816

-- 
2.29.2