[PATCH v4] git-am: add option to extract email Message-Id: tag into commit log

[Avi Kivity <avi@cloudius-systems.com>]

Some workflows prefer to track exactly which email message was used to
generate a commit.  This can be used, for example, to generate an
automated acknowledgement when a patch is committed as a response to
the patch email, or as a reference to the thread which introduced the
patch.

Support this by adding a --message-id option (abbreviated as -m) to
git-am, which will then extract the message ID and append it to the
email commit log.

Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
---

v4: adjust coding style
    recover message_id variable after a resumed git-am
    use sane_grep
    drop unneeded grep error handling

v3: remove bashism and unneeded quoting

v2: adjust to pass test suite (t5100)

 Documentation/git-am.txt |  6 ++++++
 builtin/mailinfo.c       |  2 +-
 git-am.sh                | 14 +++++++++++++-
 t/t5100/info0004         |  1 +
 t/t5100/info0005         |  1 +
 t/t5100/info0012         |  1 +
 6 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-am.txt b/Documentation/git-am.txt
index 9adce37..8a251a1 100644
--- a/Documentation/git-am.txt
+++ b/Documentation/git-am.txt
@@ -15,6 +15,7 @@ SYNOPSIS
 	 [--whitespace=<option>] [-C<n>] [-p<n>] [--directory=<dir>]
 	 [--exclude=<path>] [--include=<path>] [--reject] [-q | --quiet]
 	 [--[no-]scissors] [-S[<keyid>]] [--patch-format=<format>]
+	 [--message-id]
 	 [(<mbox> | <Maildir>)...]
 'git am' (--continue | --skip | --abort)
 
@@ -121,6 +122,11 @@ default.   You can use `--no-utf8` to override this.
 	user to lie about the author date by using the same
 	value as the committer date.
 
+-m::
+--message-id::
+	Extract the Message-Id: header from the e-mail and
+	append it to the commit message's tag stanza.
+
 --skip::
 	Skip the current patch.  This is only meaningful when
 	restarting an aborted patch.
diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index cf11c8d..f1e1fed 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -278,7 +278,7 @@ static void cleanup_space(struct strbuf *sb)
 
 static void decode_header(struct strbuf *line);
 static const char *header[MAX_HDR_PARSED] = {
-	"From","Subject","Date",
+	"From","Subject","Date","Message-Id"
 };
 
 static inline int cmp_header(const struct strbuf *line, const char *hdr)
diff --git a/git-am.sh b/git-am.sh
index ee61a77..fd0181f 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -39,6 +39,7 @@ committer-date-is-author-date    lie about committer date
 ignore-date     use current timestamp for author date
 rerere-autoupdate update the index with reused conflict resolution if possible
 S,gpg-sign?     GPG-sign commits
+m,message-id    copy the Message-Id: header to the commit's tag stanza
 rebasing*       (internal use for git-rebase)"
 
 . git-sh-setup
@@ -371,7 +372,7 @@ split_patches () {
 prec=4
 dotest="$GIT_DIR/rebase-apply"
 sign= utf8=t keep= keepcr= skip= interactive= resolved= rebasing= abort=
-resolvemsg= resume= scissors= no_inbody_headers=
+resolvemsg= resume= scissors= no_inbody_headers= message_id=
 git_apply_opt=
 committer_date_is_author_date=
 ignore_date=
@@ -442,6 +443,8 @@ it will be removed. Please do not use it anymore."
 		gpg_sign_opt=-S ;;
 	--gpg-sign=*)
 		gpg_sign_opt="-S${1#--gpg-sign=}" ;;
+	-m|--message-id)
+		message_id=t ;;
 	--)
 		shift; break ;;
 	*)
@@ -565,6 +568,7 @@ Use \"git am --abort\" to remove it.")"
 	echo " $git_apply_opt" >"$dotest/apply-opt"
 	echo "$threeway" >"$dotest/threeway"
 	echo "$sign" >"$dotest/sign"
+	echo "$message_id" >"$dotest/message-id"
 	echo "$utf8" >"$dotest/utf8"
 	echo "$keep" >"$dotest/keep"
 	echo "$scissors" >"$dotest/scissors"
@@ -651,6 +655,10 @@ then
 else
 	SIGNOFF=
 fi
+if test "$(cat "$dotest/message-id")" = t
+then
+	message_id=t
+fi
 
 last=$(cat "$dotest/last")
 this=$(cat "$dotest/next")
@@ -757,6 +765,10 @@ To restore the original branch and stop patching run \"\$cmdline --abort\"."
 		then
 			cat "$dotest/msg-clean"
 		fi
+		if test t = "$message_id"
+		then
+			sane_grep ^Message-Id: "$dotest/info"
+		fi
 		if test '' != "$ADD_SIGNOFF"
 		then
 			echo "$ADD_SIGNOFF"
diff --git a/t/t5100/info0004 b/t/t5100/info0004
index 616c309..f7e2983 100644
--- a/t/t5100/info0004
+++ b/t/t5100/info0004
@@ -2,4 +2,5 @@ Author: YOSHIFUJI Hideaki / 吉藤英明
 Email: yoshfuji@linux-ipv6.org
 Subject: GIT: Try all addresses for given remote name
 Date: Thu, 21 Jul 2005 09:10:36 -0400 (EDT)
+Message-Id: <20050721.091036.01119516.yoshfuji@linux-ipv6.org>
 
diff --git a/t/t5100/info0005 b/t/t5100/info0005
index 46a46fc..592388f 100644
--- a/t/t5100/info0005
+++ b/t/t5100/info0005
@@ -2,4 +2,5 @@ Author: David Kågedal
 Email: davidk@lysator.liu.se
 Subject: Fixed two bugs in git-cvsimport-script.
 Date: Mon, 15 Aug 2005 20:18:25 +0200
+Message-Id: <u5tacjjdpxq.fsf@lysator.liu.se>
 
diff --git a/t/t5100/info0012 b/t/t5100/info0012
index ac1216f..b5d89a1 100644
--- a/t/t5100/info0012
+++ b/t/t5100/info0012
@@ -2,4 +2,5 @@ Author: Dmitriy Blinov
 Email: bda@mnsspb.ru
 Subject: Изменён список пакетов необходимых для сборки
 Date: Wed, 12 Nov 2008 17:54:41 +0300
+Message-Id: <1226501681-24923-1-git-send-email-bda@mnsspb.ru>
 
-- 
1.9.3