am: ignore leading whitespace before patch

Some web-based email clients prepend whitespace to raw message
transcripts to workaround content-sniffing in some browsers.  Adjust
the patch format detection logic to ignore leading whitespace.

So now you can apply patches from GMail with "git am" in three steps:

 1. choose "show original"
 2. tell the browser to "save as" (for example by pressing Ctrl+S)
 3. run "git am" on the saved file

This fixes a regression introduced by v1.6.4-rc0~15^2~2 (git-am
foreign patch support: autodetect some patch formats, 2009-05-27).
GMail support was first introduced to "git am" by v1.5.4-rc0~274^2
(Make mailsplit and mailinfo strip whitespace from the start of the
input, 2007-11-01).

Signed-off-by: David Barr <davidbarr@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/git-am.sh b/git-am.sh
index 463c741dfc..c8422dbe6e 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -196,10 +196,15 @@ check_patch_format () {
 		return 0
 	fi
 
-	# otherwise, check the first few lines of the first patch to try
-	# to detect its format
+	# otherwise, check the first few non-blank lines of the first
+	# patch to try to detect its format
 	{
-		read l1
+		# Start from first line containing non-whitespace
+		l1=
+		while test -z "$l1"
+		do
+			read l1
+		done
 		read l2
 		read l3
 		case "$l1" in