Merge branch 'tr/format-patch-thread'

* tr/format-patch-thread:
  format-patch: support deep threading
  format-patch: thread as reply to cover letter even with in-reply-to
  format-patch: track several references
  format-patch: threading test reactivation

Conflicts:
	builtin-log.c

Documentation/config.txt

@@ -677,6 +677,16 @@ format.pretty::
 	See linkgit:git-log[1], linkgit:git-show[1],
 	linkgit:git-whatchanged[1].
 
+format.thread::
+	The default threading style for 'git-format-patch'.  Can be
+	either a boolean value, `shallow` or `deep`.  'Shallow'
+	threading makes every mail a reply to the head of the series,
+	where the head is chosen from the cover letter, the
+	`\--in-reply-to`, and the first patch mail, in this order.
+	'Deep' threading makes every mail a reply to the previous one.
+	A true boolean value is the same as `shallow`, and a false
+	value disables threading.
+
 gc.aggressiveWindow::
 	The window size parameter used in the delta compression
 	algorithm used by 'git-gc --aggressive'.  This defaults

Documentation/git-format-patch.txt

@@ -127,10 +127,18 @@ include::diff-options.txt[]
 	which is the commit message and the patch itself in the
 	second part, with "Content-Disposition: inline".
 
---thread::
+--thread[=<style>]::
 	Add In-Reply-To and References headers to make the second and
 	subsequent mails appear as replies to the first.  Also generates
 	the Message-Id header to reference.
++
+The optional <style> argument can be either `shallow` or `deep`.
+'Shallow' threading makes every mail a reply to the head of the
+series, where the head is chosen from the cover letter, the
+`\--in-reply-to`, and the first patch mail, in this order.  'Deep'
+threading makes every mail a reply to the previous one.  If not
+specified, defaults to the 'format.thread' configuration, or `shallow`
+if that is not set.
 
 --in-reply-to=Message-Id::
 	Make the first mail (or all the mails with --no-thread) appear as a

builtin-log.c

@@ -17,6 +17,7 @@
 #include "run-command.h"
 #include "shortlog.h"
 #include "remote.h"
+#include "string-list.h"
 
 /* Set a default date-time format for git log ("log.date" config variable) */
 static const char *default_date_mode = NULL;
@@ -461,6 +462,10 @@ static void add_header(const char *value)
 	extra_hdr[extra_hdr_nr++] = xstrndup(value, len);
 }
 
+#define THREAD_SHALLOW 1
+#define THREAD_DEEP 2
+static int thread = 0;
+
 static int git_format_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "format.headers")) {
@@ -497,7 +502,18 @@ static int git_format_config(const char *var, const char *value, void *cb)
 			default_attach = xstrdup(git_version_string);
 		return 0;
 	}
-
+	if (!strcmp(var, "format.thread")) {
+		if (value && !strcasecmp(value, "deep")) {
+			thread = THREAD_DEEP;
+			return 0;
+		}
+		if (value && !strcasecmp(value, "shallow")) {
+			thread = THREAD_SHALLOW;
+			return 0;
+		}
+		thread = git_config_bool(var, value) && THREAD_SHALLOW;
+		return 0;
+	}
 
 	return git_log_config(var, value, cb);
 }
@@ -776,7 +792,6 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	int numbered_files = 0;		/* _just_ numbers */
 	int subject_prefix = 0;
 	int ignore_if_in_upstream = 0;
-	int thread = 0;
 	int cover_letter = 0;
 	int boundary_count = 0;
 	int no_binary_diff = 0;
@@ -878,8 +893,13 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		}
 		else if (!strcmp(argv[i], "--ignore-if-in-upstream"))
 			ignore_if_in_upstream = 1;
-		else if (!strcmp(argv[i], "--thread"))
-			thread = 1;
+		else if (!strcmp(argv[i], "--thread")
+			|| !strcmp(argv[i], "--thread=shallow"))
+			thread = THREAD_SHALLOW;
+		else if (!strcmp(argv[i], "--thread=deep"))
+			thread = THREAD_DEEP;
+		else if (!strcmp(argv[i], "--no-thread"))
+			thread = 0;
 		else if (!prefixcmp(argv[i], "--in-reply-to="))
 			in_reply_to = argv[i] + 14;
 		else if (!strcmp(argv[i], "--in-reply-to")) {
@@ -1030,8 +1050,12 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		numbered = 1;
 	if (numbered)
 		rev.total = total + start_number - 1;
-	if (in_reply_to)
-		rev.ref_message_id = clean_message_id(in_reply_to);
+	if (in_reply_to || thread || cover_letter)
+		rev.ref_message_ids = xcalloc(1, sizeof(struct string_list));
+	if (in_reply_to) {
+		const char *msgid = clean_message_id(in_reply_to);
+		string_list_append(msgid, rev.ref_message_ids);
+	}
 	if (cover_letter) {
 		if (thread)
 			gen_message_id(&rev, "cover");
@@ -1050,15 +1074,33 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			/* Have we already had a message ID? */
 			if (rev.message_id) {
 				/*
-				 * If we've got the ID to be a reply
-				 * to, discard the current ID;
-				 * otherwise, make everything a reply
-				 * to that.
+				 * For deep threading: make every mail
+				 * a reply to the previous one, no
+				 * matter what other options are set.
+				 *
+				 * For shallow threading:
+				 *
+				 * Without --cover-letter and
+				 * --in-reply-to, make every mail a
+				 * reply to the one before.
+				 *
+				 * With --in-reply-to but no
+				 * --cover-letter, make every mail a
+				 * reply to the <reply-to>.
+				 *
+				 * With --cover-letter, make every
+				 * mail but the cover letter a reply
+				 * to the cover letter.  The cover
+				 * letter is a reply to the
+				 * --in-reply-to, if specified.
 				 */
-				if (rev.ref_message_id)
+				if (thread == THREAD_SHALLOW
+				    && rev.ref_message_ids->nr > 0
+				    && (!cover_letter || rev.nr > 1))
 					free(rev.message_id);
 				else
-					rev.ref_message_id = rev.message_id;
+					string_list_append(rev.message_id,
+							   rev.ref_message_ids);
 			}
 			gen_message_id(&rev, sha1_to_hex(commit->object.sha1));
 		}

log-tree.c

@@ -6,6 +6,7 @@
 #include "log-tree.h"
 #include "reflog-walk.h"
 #include "refs.h"
+#include "string-list.h"
 
 struct decoration name_decoration = { "object names" };
 
@@ -211,9 +212,13 @@ void log_write_email_headers(struct rev_info *opt, const char *name,
 		printf("Message-Id: <%s>\n", opt->message_id);
 		graph_show_oneline(opt->graph);
 	}
-	if (opt->ref_message_id) {
-		printf("In-Reply-To: <%s>\nReferences: <%s>\n",
-		       opt->ref_message_id, opt->ref_message_id);
+	if (opt->ref_message_ids && opt->ref_message_ids->nr > 0) {
+		int i, n;
+		n = opt->ref_message_ids->nr;
+		printf("In-Reply-To: <%s>\n", opt->ref_message_ids->items[n-1].string);
+		for (i = 0; i < n; i++)
+			printf("%s<%s>\n", (i > 0 ? "\t" : "References: "),
+			       opt->ref_message_ids->items[i].string);
 		graph_show_oneline(opt->graph);
 	}
 	if (opt->mime_boundary) {

revision.h

@@ -89,7 +89,7 @@ struct rev_info {
 	int		nr, total;
 	const char	*mime_boundary;
 	char		*message_id;
-	const char	*ref_message_id;
+	struct string_list *ref_message_ids;
 	const char	*add_signoff;
 	const char	*extra_headers;
 	const char	*log_reencode;