Re: git log for a merged branch

[Michele Ballabio <barra_cuda@katamail.com>]

On Wednesday 08 September 2010, Stephen Bash wrote:
> Assume I have a release branch with bug fixes that is tagged at the end of
> the release cycle (let's call the tag tagFoo).  The release branch then
> gets merged back into mainline development (call the branch mainline), and
> the release branch is deleted.  If I want to see the commits (bug fixes)
> performed on the release branch, how do I do it?
> 
> I don't think
>    git log mainline..tagFoo
> works because all the commits of tagFoo are now reachable by mainline
> thanks to the merge.  Is there a simple way to express this concept?
> 
> Obviously in a pinch a simple
>    git log tagFoo
> will give you everything back to the beginning of time, but I think that's
> suboptimal...

Let's call the merge commit "mergecmt". The commit where the "release" branch
branched off is

	git merge-base mergecmt^1 mergecmt^2

... where mergecmt^1 is the first parent of the merge (usually on the
"mainline" branch) and mergecmt^2 is the second parent, which usually(*)
refers to the "release" branch (in this case, tagFoo).

So

	git log $(git merge-base mergecmt^1 mergecmt^2)..mergecmt^2

is what you want.

> To complicate things a bit more, in the real world there may be multiple
> merges from the release branch to mainline during the life of the release
> branch, so any solution that also deals with that would be outstanding
> (probably at the cost of additional complexity?)

Maybe something like:

	for i in $(git rev-list --merges last_interesting_tag..mainline)
	do
		git log $(git merge-base $i^1 $i^2)..$i^2
	done

... or maybe using GIT_PAGER='':

	for i in $(git rev-list --merges last_interesting_tag..mainline)
	do
		GIT_PAGER='' git log $(git merge-base $i^1 $i^2)..$i^2
	done

(*) I don't remember the details, but if you do the standard "git pull"
or "git merge" and don't use the plumbing commands in a weird way to badly
reimplement "merge" or "pull", you should be safe. Others may want to
comment on this, though.