bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Wolfgang Schnerring]

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Hello,

vc-svn has the useful behaviour (via vc-svn-find-file-hook) that when
you visit a file with conflicts, it drops you into smerge-mode, and
automatically marks the file as resolved once you've removed all
conflict markers. This makes for a very seamless editing experience. :-)

It would be nice if vc-hg did the same. I guess most of the behaviour
can be lifted straight from vc-svn, however I didn't find anything to
suggest that vc-hg talks to "hg resolve -l" at the moment, which is
needed to find out whether the current file is conflicted. So I guess
that would be the starting point.

My elisp is rather weak, so I probably won't be of much help here, but
do let me know if there's something I can do.

Wolfgang

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bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Glenn Morris]

Wolfgang Schnerring wrote:

> vc-svn has the useful behaviour (via vc-svn-find-file-hook) that when
> you visit a file with conflicts, it drops you into smerge-mode, and
> automatically marks the file as resolved once you've removed all
> conflict markers. This makes for a very seamless editing experience. :-)
>
> It would be nice if vc-hg did the same.

I guess you need to get hg to generate standard conflict markers. Ref:

https://lists.ubuntu.com/archives/bazaar/2012q1/074313.html

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Glenn Morris]

Glenn Morris wrote:

> I guess you need to get hg to generate standard conflict markers. Ref:

Actually I guess vc-hg would need some changes too.

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Wolfgang Schnerring]

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* Glenn Morris <rgm@gnu.org> [2012-02-03 12:11]:
> Glenn Morris wrote:
> > I guess you need to get hg to generate standard conflict markers. Ref:

You could configure diff3 as the default merge program.
However, in my experience, using smerge-mode on the "internal:merge"
results of hg worked, too.
 
> Actually I guess vc-hg would need some changes too.

Yep, I guess you'd need changes on both ends.

Wolfgang

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bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Stefan Monnier]

>> > I guess you need to get hg to generate standard conflict markers. Ref:
> You could configure diff3 as the default merge program.
> However, in my experience, using smerge-mode on the "internal:merge"
> results of hg worked, too.

So you're saying that hg uses standard conflict markers in its
internal:merge code?  Wonderful.

>> Actually I guess vc-hg would need some changes too.
> Yep, I guess you'd need changes on both ends.

Apparently only vc-hg.el needs to be changed, then.


        Stefan

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Wolfgang Schnerring]

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* Stefan Monnier <monnier@iro.umontreal.ca> [2012-02-03 14:32]:
> So you're saying that hg uses standard conflict markers in its
> internal:merge code?  Wonderful.

I've just double-checked: yes, it does. Here's an example of a file
with conflicts:

<<<<<<< local
foo = baz
=======
foo = qux
>>>>>>> other

This matches the markers defined in smerge-mode, and invoking
smerge-mode manually on the example file works just fine, just as I
remembered.

> >> Actually I guess vc-hg would need some changes too.
> > Yep, I guess you'd need changes on both ends.
> 
> Apparently only vc-hg.el needs to be changed, then.

Yup, this brings me back to my original chain of thought: vc-hg needs
to learn to detect conflicted files, and the vc-find-file-hook needs
to be ported/abstracted from vc-svn.

Wolfgang

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bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Stefan Monnier]

>> So you're saying that hg uses standard conflict markers in its
>> internal:merge code?  Wonderful.
> I've just double-checked: yes, it does. Here's an example of a file
> with conflicts:

> <<<<<<< local
> foo = baz
> =======
> foo = qux
>>>>>>>> other

> This matches the markers defined in smerge-mode, and invoking
> smerge-mode manually on the example file works just fine, just as I
> remembered.

>> >> Actually I guess vc-hg would need some changes too.
>> > Yep, I guess you'd need changes on both ends.
>> 
>> Apparently only vc-hg.el needs to be changed, then.

> Yup, this brings me back to my original chain of thought: vc-hg needs
> to learn to detect conflicted files, and the vc-find-file-hook needs
> to be ported/abstracted from vc-svn.

You can also check vc-bzr.el which has similar code.


        Stefan

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Stefan Monnier]

>> vc-svn has the useful behaviour (via vc-svn-find-file-hook) that when
>> you visit a file with conflicts, it drops you into smerge-mode, and
>> automatically marks the file as resolved once you've removed all
>> conflict markers. This makes for a very seamless editing experience. :-)
>> It would be nice if vc-hg did the same.
> I guess you need to get hg to generate standard conflict markers. Ref:
> https://lists.ubuntu.com/archives/bazaar/2012q1/074313.html

Note: I do not know that hg uses non-standard conflict markers.


        Stefan

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Glenn Morris]

Wolfgang Schnerring wrote:

> vc-svn has the useful behaviour (via vc-svn-find-file-hook) that when
> you visit a file with conflicts, it drops you into smerge-mode, and
> automatically marks the file as resolved once you've removed all
> conflict markers. This makes for a very seamless editing experience. :-)
>
> It would be nice if vc-hg did the same. I guess most of the behaviour
> can be lifted straight from vc-svn, however I didn't find anything to
> suggest that vc-hg talks to "hg resolve -l" at the moment, which is
> needed to find out whether the current file is conflicted. So I guess
> that would be the starting point.

Maybe something like this, copied from vc-bzr?

The detection of a conflict is poor and Needs Work. With bzr we have
.BASE, .OTHER, and .THIS files present. With hg, conflicts don't even
seem to show up in "hg status". It's probably not a good idea to call
"hg resolve -l" on every single visit to an hg controlled file.
Nor is it probably a good idea to search the entirety of every file for
<<<< markers without some other clue suggesting a conflict. I used .orig
files because I seemed to get one in my two minutes playing with hg.
These don't seem to get cleaned up on hg resolve, so maybe
vc-hg-resolve-when-done should do that too? However, .orig is a very
vague, general file name.

*** lisp/vc/vc-hg.el	2012-07-19 14:38:01 +0000
--- lisp/vc/vc-hg.el	2012-12-01 01:01:18 +0000
***************
*** 464,469 ****
--- 464,492 ----
          (vc-hg-command t 0 file "cat" "-r" rev)
        (vc-hg-command t 0 file "cat")))))
  
+ (defun vc-hg-resolve-when-done ()
+   "Call \"hg resolve -m\" if the conflict markers have been removed."
+   (save-excursion
+     (goto-char (point-min))
+     (unless (re-search-forward "^<<<<<<< " nil t)
+       (vc-hg-command nil 0 buffer-file-name "resolve" "-m")
+       ;; Remove the hook so that it is not called multiple times.
+       (remove-hook 'after-save-hook 'vc-hg-resolve-when-done t))))
+ 
+ (defun vc-hg-find-file-hook ()
+   (when (and buffer-file-name
+              (file-exists-p (concat buffer-file-name ".orig"))
+              ;; FIXME: We should check that "hg resolve -l" says "U".
+              ;; If "hg resolve -l" says there's a conflict but there are no
+              ;; conflict markers, it's not clear what we should do.
+              (save-excursion
+                (goto-char (point-min))
+                (re-search-forward "^<<<<<<< " nil t)))
+     (smerge-start-session)
+     (add-hook 'after-save-hook 'vc-hg-resolve-when-done nil t)
+     (message "There are unresolved conflicts in this file")))
+ 
+ 
  ;; Modeled after the similar function in vc-bzr.el
  (defun vc-hg-workfile-unchanged-p (file)
    (eq 'up-to-date (vc-hg-state file)))

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Stefan Monnier]

> The detection of a conflict is poor and Needs Work. With bzr we have

Maybe we should ask on a Mercurial list how it can be done (and turn it
into a feature request if there's no good answer)?


        Stefan

bug#10709: Feature request: vc-hg should activate smerge-mode for conflicts

[Glenn Morris]

Stefan Monnier wrote:

>> The detection of a conflict is poor and Needs Work. With bzr we have
>
> Maybe we should ask on a Mercurial list how it can be done (and turn it
> into a feature request if there's no good answer)?

AFAICS they have set their face against it, eg

http://bz.selenic.com/show_bug.cgi?id=2724  # RESOLVED FIXED

I think checking for state = 'edited, plus .orig file, plus conflict
markers is good enough for a start, so I installed that to trunk and we
can see how it works out for people.

BTW, I think this stuff should be abstracted to a general
vc-find-file-hook/after-save-hook that calls vc-BACKEND-conflicted-p.