diff: unify calls to diffline

diffline was called from trydiff for binary diffs and from unidiff
for text diffs. In this patch we unify those calls into one.

diffline is also a header, not part of diff mechanisms, so it makes
sense to remove that responsibility from the mdiff module. In
upcoming patches we will move diffline to patch module and
keep grouping responsibilities.

mercurial/mdiff.py

@@ -156,7 +156,7 def diffline(revs, a, b, opts):
         parts.append(a)
     return ' '.join(parts) + '\n'
 
-def unidiff(a, ad, b, bd, fn1, fn2, r=None, opts=defaultopts):
+def unidiff(a, ad, b, bd, fn1, fn2, opts=defaultopts):
     def datetag(date, fn=None):
         if not opts.git and not opts.nodates:
             return '\t%s\n' % date
@@ -207,9 +207,6 def unidiff(a, ad, b, bd, fn1, fn2, r=No
         if l[ln][-1] != '\n':
             l[ln] += "\n\ No newline at end of file\n"
 
-    if r:
-        l.insert(0, diffline(r, fn1, fn2, opts))
-
     return "".join(l)
 
 # creates a headerless unified diff

mercurial/patch.py

@@ -1746,17 +1746,17 def trydiff(repo, revs, ctx1, ctx2, modi
                         dodiff = 'binary'
                 elif binary or nflag != oflag:
                     losedatafn(f)
-            if opts.git:
-                header.insert(0, mdiff.diffline(revs, join(a), join(b), opts))
 
         if dodiff:
+            if opts.git or revs:
+                header.insert(0, mdiff.diffline(revs, join(a), join(b), opts))
             if dodiff == 'binary':
                 text = mdiff.b85diff(to, tn)
             else:
                 text = mdiff.unidiff(to, date1,
                                     # ctx2 date may be dynamic
                                     tn, util.datestr(ctx2.date()),
-                                    join(a), join(b), revs, opts=opts)
+                                    join(a), join(b), opts=opts)
             if header and (text or len(header) > 1):
                 yield ''.join(header)
             if text: