Infer a --repository argument from command arguments when reasonable.

In particular: if invoked without -R from a CWD not inside a repo, having been
passed one or more file paths as command arguments, where the nearest enclosing
repo of all of those paths is the same, quietly infer a -R option for that repo.
Otherwise abort with an error message as before.

mercurial/dispatch.py

@@ -150,8 +150,7 b' def _runcatch(ui, args):'
 
     return -1
 
-def _findrepo():
-    p = os.getcwd()
+def _findrepo(p):
     while not os.path.isdir(os.path.join(p, ".hg")):
         oldp, p = p, os.path.dirname(p)
         if p == oldp:
@@ -254,7 +253,7 b' def _dispatch(ui, args):'
         os.chdir(cwd[-1])
 
     # read the local repository .hgrc into a local ui object
-    path = _findrepo() or ""
+    path = _findrepo(os.getcwd()) or ""
     if not path:
         lui = ui
     if path:
@@ -345,6 +344,11 b' def _dispatch(ui, args):'
             ui.setconfig("bundle", "mainreporoot", repo.root)
         except hg.RepoError:
             if cmd not in commands.optionalrepo.split():
+                if args and not path: # try to infer -R from command args
+                    repos = map(_findrepo, args)
+                    guess = repos[0]
+                    if guess and repos.count(guess) == len(repos):
+                        return _dispatch(ui, ['--repository', guess] + fullargs)
                 if not path:
                     raise hg.RepoError(_("There is no Mercurial repository here"
                                          " (.hg not found)"))

tests/test-globalopts

@@ -25,6 +25,13 b' echo %% -R/--repository'
 hg -R a tip
 hg --repository b tip
 
+echo %% implicit -R
+hg ann a/a
+hg ann a/a a/a
+hg ann a/a b/b
+hg -R b ann a/a
+hg log
+
 echo %% abbrev of long option
 hg --repo c tip
 

tests/test-globalopts.out

@@ -24,6 +24,12 b' user: test'
 date:        Thu Jan 01 00:00:01 1970 +0000
 summary:     b
 
+%% implicit -R
+0: a
+0: a
+abort: There is no Mercurial repository here (.hg not found)!
+abort: a/a not under root
+abort: There is no Mercurial repository here (.hg not found)!
 %% abbrev of long option
 changeset:   1:b6c483daf290
 tag:         tip