ui: invoke editor for committing with HGEDITFORM environment variable

At the external editor invocation for committing, the value specified
as "editform" for "cmdutil.getcommiteditor" is in "HGEDITFORM".

This enables external editor to do own customization according to
commit types.

mercurial/cmdutil.py

@@ -2215,7 +2215,7 b' def commitforceeditor(repo, ctx, subs, f'
     # run editor in the repository root
     olddir = os.getcwd()
     os.chdir(repo.root)
-    text = repo.ui.edit(committext, ctx.user(), ctx.extra())
+    text = repo.ui.edit(committext, ctx.user(), ctx.extra(), editform=editform)
     text = re.sub("(?m)^HG:.*(\n|$)", "", text)
     os.chdir(olddir)
 

mercurial/help/config.txt

@@ -420,6 +420,10 b' For example, ``changeset.tag.remove`` cu'
 only for :hg:`tag --remove`, but ``changeset.tag`` customizes the
 commit message for :hg:`tag` regardless of ``--remove`` option.
 
+At the external editor invocation for committing, corresponding
+dot-separated list of names without ``changeset.`` prefix
+(e.g. ``commit.normal``) is in ``HGEDITFORM`` environment variable.
+
 In this section, items other than ``changeset`` can be referred from
 others. For example, the configuration to list committed files up
 below can be referred as ``{listupfiles}``::

mercurial/ui.py

@@ -728,7 +728,7 b' class ui(object):'
         if self.debugflag:
             opts['label'] = opts.get('label', '') + ' ui.debug'
             self.write(*msg, **opts)
-    def edit(self, text, user, extra={}):
+    def edit(self, text, user, extra={}, editform=None):
         (fd, name) = tempfile.mkstemp(prefix="hg-editor-", suffix=".txt",
                                       text=True)
         try:
@@ -743,6 +743,8 b' class ui(object):'
                 if label in extra:
                     environ.update({'HGREVISION': extra[label]})
                     break
+            if editform:
+                environ.update({'HGEDITFORM': editform})
 
             editor = self.geteditor()
 

tests/test-commit.t

@@ -4,7 +4,12 b' commit date test'
   $ cd test
   $ echo foo > foo
   $ hg add foo
-  $ HGEDITOR=true hg commit -m ""
+  $ cat > $TESTTMP/checkeditform.sh <<EOF
+  > env | grep HGEDITFORM
+  > true
+  > EOF
+  $ HGEDITOR="sh $TESTTMP/checkeditform.sh" hg commit -m ""
+  HGEDITFORM=commit.normal
   abort: empty commit message
   [255]
   $ hg commit -d '0 0' -m commit-1