diff: correct binary testing logic

This seems to be more correct given the table drawn in the previous patch.

Namely, "losedatafn" and "opts.git" are removed, "not opts.text" is added.

  - losedatafn: diff output (binary) should not be affected by "losedatafn"
  - opts.git: binary testing is helpful for detecting a fast path in the
    next path. the fast path can also be used if opts.git is False
  - opts.text: if it's set, we should treat the content as non-binary

mercurial/patch.py

@@ -2540,9 +2540,9 b' def trydiff(repo, revs, ctx1, ctx2, modi'
             content2 = fctx2.data()
             if opts.git or losedatafn:
                 flag2 = ctx2.flags(f2)
-        binary = False
-        if opts.git or losedatafn:
-            binary = any(f.isbinary() for f in [fctx1, fctx2] if f is not None)
+        # if binary is True, output "summary" or "base85", but not "text diff"
+        binary = not opts.text and any(f.isbinary()
+                                       for f in [fctx1, fctx2] if f is not None)
 
         if losedatafn and not opts.git:
             if (binary or
@@ -2595,7 +2595,7 b' def trydiff(repo, revs, ctx1, ctx2, modi'
         #  yes      | yes  *        *   *     | text diff | yes
         #  no       | *    *        *   *     | text diff | yes
         # [1]: hash(fctx.data()) is outputted. so fctx.data() cannot be faked
-        if binary and opts.git and not opts.nobinary and not opts.text:
+        if binary and opts.git and not opts.nobinary:
             text = mdiff.b85diff(content1, content2)
             if text:
                 header.append('index %s..%s' %