[PATCH v2 14/15] pretty: introduce get_pretty_userformat

[Ramkumar Ramachandra <artagnon@gmail.com>]

This helper function is intended to be used by callers implementing
--pretty themselves; it parses pretty.* configuration variables
recursively and hands the user-defined format back to the caller.  No
builtins are supported, as CMT_FMT_* are really only useful when
displaying commits.  Callers might like to define their own builtins in
the future.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 commit.h |  1 +
 pretty.c | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/commit.h b/commit.h
index 38dc0c0..7755282 100644
--- a/commit.h
+++ b/commit.h
@@ -113,6 +113,7 @@ extern char *logmsg_reencode(const struct commit *commit,
 			     const char *output_encoding);
 extern void logmsg_free(char *msg, const struct commit *commit);
 extern void get_commit_format(const char *arg, struct rev_info *);
+extern const char *get_pretty_userformat(const char *arg);
 extern const char *format_subject(struct strbuf *sb, const char *msg,
 				  const char *line_separator);
 extern void userformat_find_requirements(const char *fmt, struct userformat_want *w);
diff --git a/pretty.c b/pretty.c
index 28c0a72..70e4e44 100644
--- a/pretty.c
+++ b/pretty.c
@@ -174,6 +174,31 @@ void get_commit_format(const char *arg, struct rev_info *rev)
 }
 
 /*
+ * Function to parse --pretty string, lookup pretty.* configuration
+ * variables and return the format string, assuming no builtin
+ * formats.  Not limited to commits, unlike get_commit_format().
+ */
+const char *get_pretty_userformat(const char *arg)
+{
+	struct cmt_fmt_map *commit_format;
+
+	if (!arg || !*arg)
+		return NULL;
+
+	if (!prefixcmp(arg, "format:") || !prefixcmp(arg, "tformat:"))
+		return xstrdup(strchr(arg, ':' + 1));
+
+	if (strchr(arg, '%'))
+		return xstrdup(arg);
+
+	commit_format = find_commit_format(arg);
+	if (!commit_format || commit_format->format != CMIT_FMT_USERFORMAT)
+		die("invalid --pretty format: %s", arg);
+
+	return xstrdup(commit_format->user_format);
+}
+
+/*
  * Generic support for pretty-printing the header
  */
 static int get_one_line(const char *msg)
-- 
1.8.3.247.g485169c