Re: [PATCH] have merge put FETCH_HEAD data in commit message

From: Junio C Hamano <junkio@cox.net>
Date: Mar 21, 2007, 15:37 UTC
Message-ID: <7v648u38ws.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <20070321120643.GI20583@mellanox.co.il>

"Michael S. Tsirkin" <mst@dev.mellanox.co.il> writes:

Show 19 quoted lines

> Hi!
> I often like to fetch some code from others, review and
> then merge. So:
>
> git fetch <URL>
> git log -p FETCH_HEAD
> git merge FETCH_HEAD
>
> which is all good but gets me this message in commit log:
>
>     Merge commit 'FETCH_HEAD' into master
>
> which is not very informative.
> I can always fix this up with git commit --amend, but
> I'd like to avoid the extra step.
>
> Would the following patch be appropriate?
>
> Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>

Would "Hi!" and "Would the following be appropriate?" be part of the final commit log message?

I often hear from people who seems to like "fetch & merge", instead of "pull & reset ORIG_HEAD", as a workflow to avoid undesirable merging. This might largely be a matter of taste, but from philosophical point of view, fetch & merge is a sign of distrust (your default is not to merge, and you merge only when you choose to), and pull & reset is the opposite (your default is to merge, and after you inspect you may choose not to merge). Tool support to encourage the former feels somewhat wrong.

Having said that, since that comes up every now and then, I suspect it might make sense to have an optional behaviour in "git pull" that lets you say...

	$ git pull --preview $URL $refspec

which runs the following:

	. git fetch
        . git log -p `sed -e '/	not-for-merge	/d'\
        .	-e 's/	.*//' $GIT_DIR/FETCH_HEAD` \
        .	--not HEAD
	. asks you if you want to conclude this with a merge
	. git merge if told, otherwise abort.

The "git-log" above reads "give me the commits that are reachable from commits that are scheduled for merge but not in the current HEAD", i.e. the ones that will get merged.

Show 15 quoted lines

> diff --git a/git-merge.sh b/git-merge.sh
> index 8759c5a..629611b 100755
> --- a/git-merge.sh
> +++ b/git-merge.sh
> @@ -108,6 +108,10 @@ merge_name () {
>  		git-show-ref -q --verify "refs/heads/$truname" 2>/dev/null
>  	then
>  		echo "$rh		branch '$truname' (early part) of ."
> +	elif test -r "$GIT_DIR/$remote"
> +	then
> +		echo -n "$rh		"
> +		grep -v not-for-merge "$GIT_DIR/$remote"
>  	else
>  		echo "$rh		commit '$remote'"
>  	fi

This 'not-for-merge' grep is only good while merging FETCH_HEAD, and will not work for any other random stuff in "$GIT_DIR", so at least it should be more specific, not just checking if it is the name of a readable file in $GIT_DIR. Somebody might find good usecases for doing "git merge ORIG_HEAD" or "git merge refs/bases/tutorial", for example, and your echo & grep would do something "interesting".

Every time I added "echo -n" from my sloppiness, somebody sent in a patch to replace it with "printf". I think people on non Linux platforms would hate you for using "echo -n" (I should bug Tytso about this with git-mergetool).

I am not sure what you meant by echo -n and grep -v. Other codepaths in the if-else chain seems to create $rh (the value of the single commit being merged) followed by two tabs followed by the message, and each line in $GIT_DIR/FETCH_HEAD is already in that format, so I suspect your code duplicates the commit object name twice?

Even when you fetch more than one branch in FETCH_HEAD, using FETCH_HEAD as an SHA-1 expression always picks up the object name on the first line (iow "git merge FETCH_HEAD" will not create an Octopus), so grepping for lines without not-for-merge marker is not correct either.

You would probably want something like:

		...
	elif test FETCH_HEAD = "$remote" && test -r "$GIT_DIR/FETCH_HEAD"
        then
        	sed -e 's/	not-for-merge	/		/' \
		    -e 1q "$GIT_DIR/FETCH_HEAD"
	else
        	...