[Bug-vc-dwim] [PATCH 0/3] let vc-chlog cope better with git add -i

[Ralf Wildenhues]

Hi Jim, all,

sometimes I like to use this workflow:

1) hack away on all kinds of things,
2) use 'git add -i' to pick bits that belong in one commit,
3) 'git commit -v' those pieces,
4) go back to (2) several times until everything is committed,
5) optionally, rebase -i and merge/reorder stuff to make a nice patch
series.

In (3), I often run ':r!vc-chlog --stdin <%' which in vim pipes
the to-be-committed diff through vc-chlog, to generate a log entry
(or, from the command line: git diff --cached | vc-chlog --stdin).

Now, vc-chlog does not cope well in this situation.  Here's why: if O
is the unmodified old version, and P is the patch to be applied, then
it considers the working directory copy W to be equal to O plus P, and
tries to recreate O as W minus P.  If the premise is not fulfilled,
that can give wrong results.

I'll reply with  a patch series with a small cleanup, a new test to
expose the failure, both of which I'm pushing already; and then two
alternative ways to address the actual issue:

One introduces a new --dirty-workdir switch that lets vc-chlog
reconstruct O from W minus 'vc-dwim --diff'.  Then, P is applied on top
of O to find out what the file after the next commit would look like.
The other alternative omits the new switch and lets the new action be
the default when --stdin has been passed.

Preferences as to 3a or 3b?

Thanks,
Ralf