[PATCH 2 of 3] commit: add a -M/--reuse-message option to copy a commit message from a

[Yuya Nishihara]

On Tue, 19 May 2015 10:21:31 -0500, Matt Mackall wrote:
> On Tue, 2015-05-19 at 23:00 +0900, Yuya Nishihara wrote:
> > On Mon, 18 May 2015 13:15:16 -0500, Matt Mackall wrote:
> > > On Mon, 2015-05-18 at 10:53 -0700, Durham Goode wrote:
> > > > On 5/17/15 6:57 PM, Matt Mackall wrote:
> > > > > On Fri, 2015-05-15 at 15:54 -0700, Tony Tung wrote:
> > > > >> # HG changeset patch
> > > > >> # User Tony Tung <tonytung at fb.com>
> > > > >> # Date 1429655274 25200
> > > > >> #      Tue Apr 21 15:27:54 2015 -0700
> > > > >> # Node ID dc122dd80665762d8febe2db1a08ce00a63d5ab8
> > > > >> # Parent  18cadf9d058931ef00e5272d15cb5cf2ebc3a248
> > > > >> commit: add a -M/--reuse-message option to copy a commit message from a
> > > > >> revspec
> > > > >>
> > > > >> One way to split up a diff that includes a refactor involves resetting to
> > > > >> the ancestor, and then committing the refactor first.
> > > > > For future reference, "resetting" is git-speak that I don't understand,
> > > > > despite having looked at the git-reset manpage countless times. Please
> > > > > don't make me learn git to understand your commit messages, because git
> > > > > makes me sad. Please instead use "updating to", "reverting to", or
> > > > > whatever version of --hard/--soft/--bouncy you mean corresponds to.
> > > > >
> > > > > I vaguely recall discussing this option with Ryan, perhaps at the
> > > > > sprint. I understand the value of the feature, but I think it's below
> > > > > the threshold for UI clutter.
> > > > >
> > > > > One way of getting around that is to make a more generically useful
> > > > > feature with lower UI footprint. For instance, log historically has a
> > > > > ton of individual options to specify which revisons to show:
> > > > > --keyword/date/follow/follow-first/only-branch/only-merges/no-merges/limit/user/prune, etc.
> > > > >
> > > > > We were far past the point where things were cumbersome, the
> > > > > combinations didn't make sense, and it still wasn't expressive enough
> > > > > for all the things users wanted, and new things only worked for log.
> > > > >
> > > > > Now compare that with revsets: basically everything supports revsets,
> > > > > they're vastly more powerful and expressive, and adding new features to
> > > > > revsets doesn't clutter the help and implementation of every command.
> > > > >
> > > > > So a more "generic" version of this feature might look like this:
> > > > >
> > > > >   hg commit -u @255 -m @255 -d @255  # copy the metadata from cset 255
> > > > >
> > > > > ..but would have further reaching consequences:
> > > > >
> > > > >   hg log -d @.  # show commits with the same date as the current one
> > > > >
> > > > >   hg log -r "files(@bookmark)" # show commits that touch the same files
> > > > >
> > > > > The per-command implementation would look something like:
> > > > >
> > > > >    if opts["message"]:
> > > > >       message = cmdutil.expandopt(repo, "description", opts["message"])
> > > > >
> > > > > There are a bunch of problems with the precise form of the above,
> > > > > starting with the fact that we obviously already use "@" for other
> > > > > things, but I think it illustrates why a generic approach is more
> > > > > valuable and maintainable.
> > > > >
> > > > I like the idea of a generic solution.  What about 'hg commit -m 
> > > > {255}'?  Templates use {} to indicate "replace this with the desired 
> > > > value", so we could do the same in commands and revsets, where appropriate.
> > > 
> > > I'm actually thinking "<foo>", so there's no confusion with templates.
> 
> It's been pointed out that the potential for redirection damage is
> significant.
> 
> > This resembles "hg email --flag '{branch|upper}'". Can't we design it to be
> > compatible with the template syntax? Perhaps we can extend it to a real
> > template in future.
> >
> >   -m '{...}'       # evaluate as a template only if starts/ends with {}
> >   -m '{desc at 255}'  # infix operator "var at rev"
> >   -m '{@255}'      # prefix operator, default to {desc at 255} for -m
> 
> That seems promising. It's a bit of a problem that there's not a notion
> of "usage context" though: we'd like to be able to say "oh, we're
> talking about users here, so @255 refers to the user." So we'd need to
> pass in a default field to the helper. And we'll also need to support
> arbitrary revsets.
> 
> And @ still isn't a great choice since we used it for bookmarks. Since
> we want to support revsets, an enclosing form is probably best. Maybe
> []?

Good point. A closing bracket will allow us to parse inner expression as
a revset, not a template. So we can avoid unwanted quotes and escapes.

  '{desc[bookmark("re:[sS]table")]}'

A sad thing is that the same syntax cannot be used in the fileset.

  'set:added()[wdir()]'  # [] is glob characters

But I agree [] will be better than @.