resolve: add a flag for the default behavior of re-merging

resolve: add a flag for the default behavior of re-merging

On its own, it's not useful, but the next commit will add an hgrc
config option to make it mandatory.

There is no short option, as -r almost always means --rev and this
option doesn't seem like it would be so common as to mandate a short
option.

Differential Revision: https://phab.mercurial-scm.org/D4378

--- a/mercurial/commands.py	Sat Sep 01 02:01:55 2018 -0400
+++ b/mercurial/commands.py	Sun Aug 26 15:52:34 2018 -0400
@@ -4506,7 +4506,8 @@
     ('l', 'list', None, _('list state of files needing merge')),
     ('m', 'mark', None, _('mark files as resolved')),
     ('u', 'unmark', None, _('mark files as unresolved')),
-    ('n', 'no-status', None, _('hide status prefix'))]
+    ('n', 'no-status', None, _('hide status prefix')),
+    ('', 're-merge', None, _('re-merge files'))]
     + mergetoolopts + walkopts + formatteropts,
     _('[OPTION]... [FILE]...'),
     inferrepo=True)
@@ -4523,9 +4524,9 @@
 
     The resolve command can be used in the following ways:
 
-    - :hg:`resolve [--tool TOOL] FILE...`: attempt to re-merge the specified
-      files, discarding any previous merge attempts. Re-merging is not
-      performed for files already marked as resolved. Use ``--all/-a``
+    - :hg:`resolve [--re-merge] [--tool TOOL] FILE...`: attempt to re-merge
+      the specified files, discarding any previous merge attempts. Re-merging
+      is not performed for files already marked as resolved. Use ``--all/-a``
       to select all unresolved files. ``--tool`` can be used to specify
       the merge tool used for the given files. It overrides the HGMERGE
       environment variable and your configuration files.  Previous file
@@ -4554,11 +4555,11 @@
 
     opts = pycompat.byteskwargs(opts)
     confirm = ui.configbool('commands', 'resolve.confirm')
-    flaglist = 'all mark unmark list no_status'.split()
-    all, mark, unmark, show, nostatus = \
+    flaglist = 'all mark unmark list no_status re_merge'.split()
+    all, mark, unmark, show, nostatus, remerge = \
         [opts.get(o) for o in flaglist]
 
-    if len(list(filter(None, [show, mark, unmark]))) > 1:
+    if len(list(filter(None, [show, mark, unmark, remerge]))) > 1:
         raise error.Abort(_("too many options specified"))
     if pats and all:
         raise error.Abort(_("can't specify --all and patterns"))
@@ -4752,8 +4753,11 @@
                 for f in ms:
                     if not m(f):
                         continue
-                    flags = ''.join(['-%s ' % o[0:1] for o in flaglist
-                                                   if opts.get(o)])
+                    def flag(o):
+                        if o == 're_merge':
+                            return '--re-merge '
+                        return '-%s ' % o[0:1]
+                    flags = ''.join([flag(o) for o in flaglist if opts.get(o)])
                     hint = _("(try: hg resolve %s%s)\n") % (
                              flags,
                              ' '.join(pats))

--- a/tests/test-completion.t	Sat Sep 01 02:01:55 2018 -0400
+++ b/tests/test-completion.t	Sun Aug 26 15:52:34 2018 -0400
@@ -331,7 +331,7 @@
   phase: public, draft, secret, force, rev
   recover: 
   rename: after, force, include, exclude, dry-run
-  resolve: all, list, mark, unmark, no-status, tool, include, exclude, template
+  resolve: all, list, mark, unmark, no-status, re-merge, tool, include, exclude, template
   revert: all, date, rev, no-backup, interactive, include, exclude, dry-run
   rollback: dry-run, force
   root: 

--- a/tests/test-resolve.t	Sat Sep 01 02:01:55 2018 -0400
+++ b/tests/test-resolve.t	Sun Aug 26 15:52:34 2018 -0400
@@ -442,6 +442,18 @@
   $ hg resolve -l
   R file1
   R file2
+Testing the --re-merge flag
+  $ hg resolve --unmark file1
+  $ hg resolve -l
+  U file1
+  R file2
+  $ hg resolve --mark --re-merge
+  abort: too many options specified
+  [255]
+  $ hg resolve --re-merge --all
+  merging file1
+  warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
+  [1]
 
   $ cd ..