cmdutil: warnings not issued in cat if subrepopath overlaps

Previously a subrepository "sub" would cause no warnings to
be issued for a file "subnot/a", if it's not present in the
corresponding changeset when calling:

hg cat subnot/a

mercurial/cmdutil.py

@@ -2584,7 +2584,7 def cat(ui, repo, ctx, matcher, prefix,
     # Don't warn about "missing" files that are really in subrepos
     def badfn(path, msg):
         for subpath in ctx.substate:
-            if path.startswith(subpath):
+            if path.startswith(subpath + '/'):
                 return
         matcher.bad(path, msg)
 

tests/test-subrepo.t

@@ -60,6 +60,9 Subrepopath which overlaps with filepath
   $ hg remove -S snot/file
   not removing snot/file: file is untracked
   [1]
+  $ hg cat snot/filenot
+  snot/filenot: no such file in rev 7cf8cfea66e4
+  [1]
   $ rm -r snot
 
 Revert subrepo and test subrepo fileset keyword: