Re: git pull --rebase should use fast forward merge if possible

From

Junio C Hamano <gitster@pobox.com>

Date

Jun 29, 2016, 16:32 UTC

Message-ID

<xmqqd1n0552i.fsf@gitster.mtv.corp.google.com>

In-Reply-To

<OF95D98CB6.47969C1C-ONC1257FE1.0058D980-C1257FE1.0059986D@dakosy.de>

neuling@dakosy.de writes:

> since I have added "pull.rebase=preserve" to my global configuration I 
> wonder why "git pull" also trys to rebase if a fast forward merge is 
> possible. 
>
> A fast forward merge would speed up every pull if your local branch 
> contains no new commits and the remote branch is ahead. The result would 
> be the same. 
>
> Is it possible to change the behavior of "git pull 
> --rebase=true|preserve|interactive" to use a fast forward merge if the 
> remote branch is ahead and the local branch contains no new commits? 

Interesting.  I do not think of a reason why we shouldn't.

 contrib/examples/git-pull.sh | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/contrib/examples/git-pull.sh b/contrib/examples/git-pull.sh
index 6b3a03f..3648040 100755
--- a/contrib/examples/git-pull.sh
+++ b/contrib/examples/git-pull.sh
@@ -358,6 +358,14 @@ fi
 
 if test true = "$rebase"
 then
+	if git merge-base --is-ancestor "$orig_head" "$merge_head"
+	then
+		# We can just fast-forward, as "git rebase --no-ff"
+		# is nonsense.
+		git merge --ff-only "$merge_head"
+		exit
+	fi
+
 	o=$(git show-branch --merge-base $curr_branch $merge_head $oldremoteref)
 	if test "$oldremoteref" = "$o"
 	then