[PATCH 1 of 5 V2] diff: use fctx.isbinary() to test binary

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1493875014 25200
#      Wed May 03 22:16:54 2017 -0700
# Node ID 1db00a094f91000d89bda7ee14771fb14498c9b1
# Parent  2cfdf5241096f6c0c2d45d32b2f1a41575835025
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r 1db00a094f91
diff: use fctx.isbinary() to test binary

The end goal is to avoid calling fctx.data() when unnecessary. For example,
if diff.nobinary=1 and files are binary, the expected behavior is to print
"Binary file has changed". That could avoid reading fctx.data() sometimes.

This is mainly to enable an external LFS extension to skip expensive binary
file loading sometimes (read: most of the time with diff.nobinary=1 and
diff.text=0), without any behavior changes to mercurial (i.e. whether a file
is LFS or not does not change any behavior, LFS could be 100% transparent to
users).

diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -2524,17 +2524,21 @@ def trydiff(repo, revs, ctx1, ctx2, modi
         content1 = None
         content2 = None
+        fctx1 = None
+        fctx2 = None
         flag1 = None
         flag2 = None
         if f1:
-            content1 = getfilectx(f1, ctx1).data()
+            fctx1 = getfilectx(f1, ctx1)
+            content1 = fctx1.data()
             if opts.git or losedatafn:
                 flag1 = ctx1.flags(f1)
         if f2:
-            content2 = getfilectx(f2, ctx2).data()
+            fctx2 = getfilectx(f2, ctx2)
+            content2 = fctx2.data()
             if opts.git or losedatafn:
                 flag2 = ctx2.flags(f2)
         binary = False
         if opts.git or losedatafn:
-            binary = util.binary(content1) or util.binary(content2)
+            binary = any(f.isbinary() for f in [fctx1, fctx2] if f is not None)
 
         if losedatafn and not opts.git: