Re: merge ignores --no-commit in fast-forward case

From: Greg Price <price@ksplice.com>
Date: Sep 18, 2009, 19:47 UTC
Message-ID: <20090918194717.GA18999@dr-wily.mit.edu>
In-Reply-To: <7vocpfz4gm.fsf@alter.siamese.dyndns.org>

I've hit this issue in scripts where someone has written

  if ! git merge some-branch --no-commit; then
    # deal or have the user deal
  fi

  git commit -m '...'

intending that if the merge succeeds it has left the changes from some-branch uncommitted. And the script works, until for some reason some-branch is on top of HEAD. So Tomas is not the only person who was surprised or confused by the present behavior. =)

In this case the workaround is to add --no-ff to the command, which is effectively what the proposed change would do automatically.

Suppose we were to make such a change in 1.7.0 or a later version. What would the transition plan need to accomplish? For instance, we could print a warning every time 'merge --no-commit' does a fast-forward, and make the change in a later version -- might that suffice?

Cheers, Greg

PS - Here's one version of a documentation patch for #3.

>From 83282bbbd0c918016e71e4ff6fd8a823315fed0e Mon Sep 17 00:00:00 2001

From: Greg Price <price@ksplice.com>
Date: Fri, 18 Sep 2009 15:34:19 -0400
Subject: [PATCH] Document behavior of --no-commit on fast forward.

This behavior can be surprising, so document it.

Signed-off-by: Greg Price <price@ksplice.com>
---
 Documentation/merge-options.txt |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/Documentation/merge-options.txt
b/Documentation/merge-options.txt
index adadf8e..6015e5d 100644
--- a/Documentation/merge-options.txt
+++ b/Documentation/merge-options.txt
@@ -31,7 +31,10 @@
 --no-commit::
        Perform the merge but pretend the merge failed and do
        not autocommit, to give the user a chance to inspect and
-       further tweak the merge result before committing.
+       further tweak the merge result before committing.  If the
+       merge resolved as a fast-forward, the branch pointer will
+       be updated as usual; --no-ff can be combined with this
+       option to always preserve the branch pointer.
 
 --commit::
        Perform the merge and commit the result. This option can

-- 
1.6.3.1.499.ge7b8da