resolve: print warning when no work performed (issue4208)

Previously, if the paths specified as arguments to |hg resolve| were
invalid, they were silently ignored and a no-op would ensue.

This patch fixes that in some scenarios.

If none of the paths specified to |hg resolve| match a path that is in
mergestate, a warning will be emitted.

Ideally, a warning would be emitted for every path/pattern specified
that doesn't match anything. To achieve this would require significant
refactoring of the matching subsystem. That work is beyond the scope of
this patch series. Something is better than nothing and this patch
gets us something.

mercurial/commands.py

@@ -4934,10 +4934,13 b' def resolve(ui, repo, *pats, **opts):'
     m = scmutil.match(repo[None], pats, opts)
     ret = 0
 
+    didwork = False
     for f in ms:
         if not m(f):
             continue
 
+        didwork = True
+
         if show:
             if nostatus:
                 ui.write("%s\n" % f)
@@ -4970,6 +4973,10 b' def resolve(ui, repo, *pats, **opts):'
             util.rename(a + ".resolve", a + ".orig")
 
     ms.commit()
+
+    if not didwork and pats:
+        ui.warn(_("arguments do not match paths that need resolved\n"))
+
     return ret
 
 @command('revert',

tests/test-resolve.t

@@ -31,6 +31,10 b' resolve -l should contain an unresolved '
   $ hg resolve -l
   U file
 
+resolving an unknown path emits a warning
+  $ hg resolve -m does-not-exist
+  arguments do not match paths that need resolved
+
 resolve the failure
 
   $ echo resolved > file