diff: add a fast path to avoid loading binary contents
When diffing binary contents, with certain configs, we can show
"Binary file <name> has changed" without actual content.
That allows a fast path where we could avoid providing actual binary
contents. Note: in that case we still need to test if two contents are the
same, that's done by using "filectx.cmp", which could have its own fast
path.
--- a/mercurial/patch.py Fri May 05 17:20:32 2017 -0700
+++ b/mercurial/patch.py Wed May 03 23:50:41 2017 -0700
@@ -2532,12 +2532,10 @@
flag2 = None
if f1:
fctx1 = getfilectx(f1, ctx1)
- content1 = fctx1.data()
if opts.git or losedatafn:
flag1 = ctx1.flags(f1)
if f2:
fctx2 = getfilectx(f2, ctx2)
- content2 = fctx2.data()
if opts.git or losedatafn:
flag2 = ctx2.flags(f2)
# if binary is True, output "summary" or "base85", but not "text diff"
@@ -2595,6 +2593,25 @@
# yes | yes * * * | text diff | yes
# no | * * * * | text diff | yes
# [1]: hash(fctx.data()) is outputted. so fctx.data() cannot be faked
+ if binary and (not opts.git or (opts.git and opts.nobinary and not
+ opts.index)):
+ # fast path: no binary content will be displayed, content1 and
+ # content2 are only used for equivalent test. cmp() could have a
+ # fast path.
+ if fctx1 is not None:
+ content1 = b'\0'
+ if fctx2 is not None:
+ if fctx1 is not None and not fctx1.cmp(fctx2):
+ content2 = b'\0' # not different
+ else:
+ content2 = b'\0\0'
+ else:
+ # normal path: load contents
+ if fctx1 is not None:
+ content1 = fctx1.data()
+ if fctx2 is not None:
+ content2 = fctx2.data()
+
if binary and opts.git and not opts.nobinary:
text = mdiff.b85diff(content1, content2)
if text: