trydiff: make 'revs' ignored if opts.git is set

Instead of setting revs=None to prevent the call to diffline() when
opts.git is set, explicitly do not call the function in the git case.

mercurial/patch.py

@@ -1772,9 +1772,6 b' def trydiff(repo, revs, ctx1, ctx2, modi'
 
     copyto = dict([(v, k) for k, v in copy.items()])
 
-    if opts.git:
-        revs = None
-
     addedset, removedset = set(added), set(removed)
     # Fix up  added, since merged-in additions appear as
     # modifications during merges
@@ -1845,9 +1842,7 b' def trydiff(repo, revs, ctx1, ctx2, modi'
         path1 = posixpath.join(prefix, f1)
         path2 = posixpath.join(prefix, f2)
         header = []
-        if revs:
-            header.append(diffline(path1, revs))
-        elif opts.git:
+        if opts.git:
             header.append('diff --git %s%s %s%s\n' %
                           (aprefix, path1, bprefix, path2))
             if content1 is None: # added
@@ -1862,6 +1857,8 b' def trydiff(repo, revs, ctx1, ctx2, modi'
                 if op is not None:
                     header.append('%s from %s\n' % (op, path1))
                     header.append('%s to %s\n' % (op, path2))
+        elif revs:
+            header.append(diffline(path1, revs))
 
         if binarydiff and not opts.nobinary:
             text = mdiff.b85diff(content1, content2)