Re: [PATCH v2] format-patch: allow a non-integral version numbers

diff --git a/Documentation/git-format-patch.txt b/Documentation/git-format-patch.txt
index 3e49bf221087..f10fa6527f5f 100644
--- a/Documentation/git-format-patch.txt
+++ b/Documentation/git-format-patch.txt

@@ -22,6 +22,7 @@ SYNOPSIS
 		   [--cover-from-description=<mode>]
 		   [--rfc] [--subject-prefix=<subject prefix>]
 		   [(--reroll-count|-v) <n>]
+		   [--previous-count=<n>]
 		   [--to=<email>] [--cc=<email>]
 		   [--[no-]cover-letter] [--quiet]
 		   [--[no-]encode-email-headers]

@@ -221,6 +222,15 @@ populated with placeholder text.
 	`--subject-prefix` option) has ` v<n>` appended to it.  E.g.
 	`--reroll-count=4` may produce `v4-0001-add-makefile.patch`
 	file that has "Subject: [PATCH v4 1/20] Add makefile" in it.
+	now can support non-integrated version number like `-v1.1`.
+
+--previous-count=<n>::
+	Under the premise that we have used `--reroll-count=<n>`,
+	we can use `--previous-count=<n>` to specify the previous
+	version number. E.g. When we use the `--range-diff` or
+	`--interdiff` option and combine with `-v2.3 --previous-count=2.2`,
+	"Interdiff against v2.2:" or "Range-diff against v2.2:"
+	will be output in the patch.
 
 --to=<email>::
 	Add a `To:` header to the email headers. This is in addition

diff --git a/builtin/log.c b/builtin/log.c
index f67b67d80ed1..95c95eab5393 100644
--- a/builtin/log.c
+++ b/builtin/log.c

@@ -1662,13 +1662,15 @@ static void print_bases(struct base_tree_info *bases, FILE *file)
 	oidclr(&bases->base_commit);
 }
 
-static const char *diff_title(struct strbuf *sb, int reroll_count,
-		       const char *generic, const char *rerolled)
+static const char *diff_title(struct strbuf *sb, const char *reroll_count, int reroll_count_is_integer,
+			const char*previous_count, const char *generic, const char *rerolled)
 {
-	if (reroll_count <= 0)
+	if (!reroll_count || (!reroll_count_is_integer && !previous_count))
 		strbuf_addstr(sb, generic);
-	else /* RFC may be v0, so allow -v1 to diff against v0 */
-		strbuf_addf(sb, rerolled, reroll_count - 1);
+	else if (reroll_count_is_integer)/* RFC may be v0, so allow -v1 to diff against v0 */
+		strbuf_addf(sb, rerolled, atoi(reroll_count) - 1);
+	else if (previous_count)
+		strbuf_addf(sb, rerolled, previous_count);
 	return sb->buf;
 }

@@ -1717,7 +1719,9 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	struct strbuf buf = STRBUF_INIT;
 	int use_patch_format = 0;
 	int quiet = 0;
-	int reroll_count = -1;
+	int reroll_count_is_integer = 0;
+	const char *reroll_count = NULL;
+	const char *previous_count = NULL;

 	char *cover_from_description_arg = NULL;
 	char *branch_name = NULL;
 	char *base_commit = NULL;

@@ -1751,8 +1755,10 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 			    N_("use <sfx> instead of '.patch'")),
 		OPT_INTEGER(0, "start-number", &start_number,
 			    N_("start numbering patches at <n> instead of 1")),
-		OPT_INTEGER('v', "reroll-count", &reroll_count,
-			    N_("mark the series as Nth re-roll")),
+		OPT_STRING('v', "reroll-count", &reroll_count, N_("reroll-count"),
+			    N_("mark the series as specified version re-roll")),
+		OPT_STRING(0, "previous-count", &previous_count, N_("previous-count"),
+			    N_("specified as the last version while we use --reroll-count")),
 		OPT_INTEGER(0, "filename-max-length", &fmt_patch_name_max,
 			    N_("max length of output filename")),
 		OPT_CALLBACK_F(0, "rfc", &rev, NULL,

@@ -1861,10 +1867,20 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 
 	if (cover_from_description_arg)
 		cover_from_description_mode = parse_cover_from_description(cover_from_description_arg);
-
-	if (0 < reroll_count) {
+	if (previous_count && !reroll_count)
+		usage(_("previous-count can only used when reroll-count is used"));
+	if (reroll_count) {
 		struct strbuf sprefix = STRBUF_INIT;
-		strbuf_addf(&sprefix, "%s v%d",
+		char ch;
+		size_t i = 0 , reroll_count_len = strlen(reroll_count);
+
+		for (; i != reroll_count_len; i++) {
+			ch = reroll_count[i];
+			if(!isdigit(ch))
+				break;
+		}
+		reroll_count_is_integer = i == reroll_count_len ? 1 : 0;
+		strbuf_addf(&sprefix, "%s v%s",
 			    rev.subject_prefix, reroll_count);
 		rev.reroll_count = reroll_count;
 		rev.subject_prefix = strbuf_detach(&sprefix, NULL);