commit: explain how to abort commit in editor

mercurial/cmdutil.py

@@ -1231,6 +1231,7 b' def commitforceeditor(repo, ctx, added, '
     edittext.append("") # Empty line between message and comments.
     edittext.append(_("HG: Enter commit message."
                       "  Lines beginning with 'HG:' are removed."))
+    edittext.append("HG: Leave message empty to abort commit.")
     edittext.append("HG: --")
     edittext.append(_("HG: user: %s") % ctx.user())
     if ctx.p2():

tests/test-commit.out

@@ -108,6 +108,7 b' abort: cannot partially commit a merge ('
 
 
 HG: Enter commit message.  Lines beginning with 'HG:' are removed.
+HG: Leave message empty to abort commit.
 HG: --
 HG: user: test
 HG: branch 'default'