log: give hint when user forgets "-r"

Summary: I do this myself a lot. The "cannot follow file not in parent revision" error isn't very clear that you passed a revision instead of a file name. Add a hint that suggests "-r ..." and "-r ... -f".

Reviewed By: sggutier

Differential Revision: D54873788

fbshipit-source-id: 97549118b87b0553a54ed044ea2d9331d04e5294

eden/scm/sapling/cmdutil.py

@@ -3045,8 +3045,14 @@ def strategy_follow():
                     if os.path.exists(repo.wjoin(f)):
                         continue
                     else:
+                        hint = None
+                        if len(pats) == 1 and pats[0] in repo:
+                            hint = _(
+                                """did you mean "@prog@ log -r '%s'", or "@prog@ log -r '%s' -f" to follow history?"""
+                            ) % (pats[0], pats[0])
                         raise error.Abort(
-                            _("cannot follow file not in parent " 'revision: "%s"') % f
+                            _("cannot follow file not in parent " 'revision: "%s"') % f,
+                            hint=hint,
                         )
 
             # follow() revset interprets its file argument as a

eden/scm/tests/test-log-hint.t

@@ -0,0 +1,34 @@
+#debugruntest-compatible
+
+  $ configure modernclient
+  $ setconfig tweakdefaults.logdefaultfollow=true
+
+  $ newclientrepo
+  $ drawdag <<EOS
+  > B
+  > |
+  > A
+  > EOS
+  $ hg go -q $B
+
+  $ hg log tip
+  abort: cannot follow file not in parent revision: "tip"
+  (did you mean "hg log -r 'tip'", or "hg log -r 'tip' -f" to follow history?)
+  [255]
+
+  $ hg log -r 'tip'
+  commit:      112478962961
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     B
+
+  $ hg log -r 'tip' -f
+  commit:      112478962961
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     B
+
+  commit:      426bada5c675
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     A