Our patch was modified a while ago to cope a bit better with git diffs
containing a/ and b/. There is still a common case where things don't
work as they should. Consider this simple patch:
diff --git a/afile b/afile
new file mode 100644
index 00000000000..9daeafb9864
--- /dev/null
+++ b/afile
@@ -0,0 +1 @@
+test
Doing 'patch < addfile' will create 'null' and 'null.orig' files with
the null file containing the string 'test', which is obviously not what
we want.
The diff below only skips 6 letters if they actually are '--- a/' or
'+++ b/' and seems to do the trick for me in various scenarios.
Index: usr.bin/patch/pch.c
===================================================================
RCS file: /var/cvs/src/usr.bin/patch/pch.c,v
retrieving revision 1.58
diff -u -p -r1.58 pch.c
--- usr.bin/patch/pch.c 30 May 2017 06:55:40 -0000 1.58
+++ usr.bin/patch/pch.c 20 Dec 2017 12:16:15 -0000
@@ -301,14 +301,16 @@ intuit_diff_type(void)
&names[OLD_FILE].exists, strippath);
else if (strnEQ(s, "--- ", 4)) {
size_t off = 4;
- if (piece_of_git && strippath == 957)
+ if (piece_of_git && strippath == 957 &&
+ strnEQ(s, "--- a/", 6))
off = 6;
names[NEW_FILE].path = fetchname(s + off,
&names[NEW_FILE].exists, strippath);
} else if (strnEQ(s, "+++ ", 4)) {
/* pretend it is the old name */
size_t off = 4;
- if (piece_of_git && strippath == 957)
+ if (piece_of_git && strippath == 957 &&
+ strnEQ(s, "+++ b/", 6))
off = 6;
names[OLD_FILE].path = fetchname(s + off,
&names[OLD_FILE].exists, strippath);
