Re: git-cherry-pick and git-commit --amend in version 1.7.6.4

Junio C Hamano [off-list ref] writes:

It's just the "commit --amend" message that says I cannot amend felt
utterly out of place, immediately after seeing "cherry-pick" that tried to
pick only one commit did _not_ even start.

After thinking about it a bit more, I am starting to think that it may
just be the error message given by "commit --amend".

If the sequence were like this:

    $ edit foo.c ;# I want to fix foo.c in the current branch "master"
    $ EDITOR=: git commit --amend ;# forgot to say "foo.c"
    $ git cherry-pick other~2 other
    [master 48882c9] frotz: update xyzzy
     Author: Jay Soffian [off-list ref]
     1 files changed, 2 insertions(+), 2 deletions(-)
    error: Your local changes to the following files would be overwritten by merge:
            foo.c
    Please, commit your changes or stash them before you can merge.
    Aborting

Then at this point, amending the commit at HEAD^ is not possible anyway,
as it is not at the tip anymore.  It is perfectly fine that

    $ git commit --amend foo.c

fails at this point.

It is just that it initially felt irritatingly wrong if I was picking only
a single commit "other" that wanted to touch foo.c, like this:

    $ edit foo.c ;# I want to fix foo.c in the current branch "master"
    $ EDITOR=: git commit --amend ;# forgot to say "foo.c"
    $ git cherry-pick other
    error: Your local changes to the following files would be overwritten by merge:
            foo.c
    Please, commit your changes or stash them before you can merge.
    Aborting

At this point, as it says "Please commit your changes", and it is very
clear that cherry-pick _correctly_ errored out without touching any of my
work, it is natural for me to expect that I can "commit --amend" to fix
my eariler mistake.

    $ EDITOR=: git commit --amend foo.c
    fatal: You are in the middle of a cherry-pick -- cannot amend.

This can only worked around halfway:

    $ rm .git/CHERRY_PICK_HEAD
    $ EDITOR=: git commit --amend foo.c
    
Things look OK so far, but then restarting the cherry-pick I wanted to do
after I fixed foo.c would fail like this:

    $ git cherry-pick other
    error: .git/sequencer already exists.
    error: A cherry-pick or revert is in progress.
    hint: Use --continue to continue the operation
    hint: or --reset to forget about it
    fatal: cherry-pick failed

Perhaps it would be a possible solution to teach "cherry-pick --reset" to
remove CHERRY_PICK_HEAD and the sequencer state, so that the above
transcript would become:

    $ edit foo.c ;# I want to fix foo.c in the current branch "master"
    $ EDITOR=: git commit --amend ;# forgot to say "foo.c"
    $ git cherry-pick other
    error: Your local changes to the following files would be overwritten by merge:
            foo.c
    Please, commit your changes or stash them before you can merge.
    Aborting
    $ EDITOR=: git commit --amend foo.c
    fatal: You are in the middle of a cherry-pick -- cannot amend.
    hint: use "git cherry-pick --reset" to discard the previous cherry-pick.
    $ git cherry-pick --reset
    $ EDITOR=: git commit --amend foo.c
    $ git cherry-pick other
    [master 48882c9] frotz: update nitfol
     Author: Jay Soffian [off-list ref]
     1 files changed, 2 insertions(+), 2 deletions(-)

At least, that looks like something we _could_ explain to the end users.