Additional plumbing commands

Additional plumbing commands

[Charles Rudolph]

I am writing some higher level git commands for
https://github.com/Originate/git-town and would like some additional
plumbing commands that can tell me

1. is there a merge in progress?
2. is there a rebase in progress?
3. is there a cherry-pick in progress?
4. are there unmerged paths?

Currently the only way I know how to do this is with "git status" and
looking for specific text.

Thanks for any and all comments.

~Charlie

Re: Additional plumbing commands

[Christian Couder]

On Tue, Jan 6, 2015 at 5:05 PM, Charles Rudolph
<charles.w.rudolph@gmail.com> wrote:
> I am writing some higher level git commands for
> https://github.com/Originate/git-town and would like some additional
> plumbing commands that can tell me
>
> 1. is there a merge in progress?
> 2. is there a rebase in progress?
> 3. is there a cherry-pick in progress?
> 4. are there unmerged paths?
>
> Currently the only way I know how to do this is with "git status" and
> looking for specific text.

You may have a look at how "contrib/completion/git-prompt.sh" does it.
It has stuff like:

        if [ -d "$g/rebase-merge" ]; then
                __git_eread "$g/rebase-merge/head-name" b
                __git_eread "$g/rebase-merge/msgnum" step
                __git_eread "$g/rebase-merge/end" total
                if [ -f "$g/rebase-merge/interactive" ]; then
                        r="|REBASE-i"
                else
                        r="|REBASE-m"
                fi
...

Cheers,
Christian.

Re: Additional plumbing commands

[Jeff King]

On Tue, Jan 06, 2015 at 06:37:34PM +0100, Christian Couder wrote:

> On Tue, Jan 6, 2015 at 5:05 PM, Charles Rudolph
> <charles.w.rudolph@gmail.com> wrote:
> > I am writing some higher level git commands for
> > https://github.com/Originate/git-town and would like some additional
> > plumbing commands that can tell me
> >
> > 1. is there a merge in progress?
> > 2. is there a rebase in progress?
> > 3. is there a cherry-pick in progress?
> > 4. are there unmerged paths?
> >
> > Currently the only way I know how to do this is with "git status" and
> > looking for specific text.
> 
> You may have a look at how "contrib/completion/git-prompt.sh" does it.
> [...]

The prompt code is rather long and knows a lot about the internal state
of $GIT_DIR. I do not think it would be a bad thing for git-status to
expose a machine-readable version of the state it discovers, and then at
least we can keep the logic in one place.

Charles, if you are interested in adding that, the wt_status_state code
in wt-status.c is the right place to start looking.

Though I think in many cases that discovering which state we are in is
only half the story that a caller wants. Knowing what each state _means_
and what operations are meaningful to perform is much trickier (e.g., if
we are in a rebase, you probably do not want to start a new rebase. But
is it wrong to cherry-pick?).

It would be nice if we could find a way to generalize in-progress
operations and what they mean for starting new operations, but that is
a much harder problem (if it is even possible at all).

-Peff

Re: Additional plumbing commands

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> ... Knowing what each state _means_
> and what operations are meaningful to perform is much trickier (e.g., if
> we are in a rebase, you probably do not want to start a new rebase. But
> is it wrong to cherry-pick?).
>
> It would be nice if we could find a way to generalize in-progress
> operations and what they mean for starting new operations, but that is
> a much harder problem (if it is even possible at all).

Very good points. Thinking aloud, to see if we can start from a few
rules of thumb.

You can be "in the middle" for two largely different reasons.

One is that the command inherently wants to give control back to
you.  Think of a case where you said "exec false" in the "rebase -i"
insn sheet, or "bisect" checked out a version for you to try.

The other is that the command wanted to continue in the ideal world,
but couldn't and stopped asking for your help.  Think of a case
where "am" stopped due to corrupt patch, "cherry-pick A..B" or
"revert" stopped due to conflicts.

In the former case, depending on the nature of the command, what are
sensible things you can do are very different (during "bisect" you
would typically not want to do anything that causes a commit
created.  During "rebase -i" you may want to run any command that
creates a commit, to insert a new one into the series).  But a good
rule of thumb would be "If I should be able to edit the working tree
file, I should also be able to do "cherry-pick --no-commit", "merge
--no-commit", "apply", etc." "If I should be able to manually
commit, I should also be able to "cherry-pick", "merge", etc.

In the latter, the _only_ reason you are given control back is to
help the interrupted operation.  So "cherry-pick --no-commit" or
"apply" in lieu of editing files manually in order to fix conflicts
should be allowed, but a random "git merge" (without --no-commit)
would not be.

So after thinking aloud for a while, I very much agree with you that
you cannot say "X is allowed but not Y" in many situations.

One thing we can say for sure is that in a middle of a multi-step
operation (e.g. rebase, range pick) is stopped for either one of the
two reasons, you cannot do another multi-step operation.  This is
not fundamental but a consequence of how the sequencing machinery is
implemented.  But other than that, it really is case-by-case and not
even command-by-command.