[PATCH 7/8] pretty: refactor parsing of magic

[Martin Ågren <martin.agren@xxxxxxxxx>]

Similar to the previous commit, pull out our parsing of initial
placeholder magic into a separate function. This helps make it a bit
easier to get an overview of `format_commit_item()`. It also represents
another small step towards separating the parsing of placeholders from
subsequent usage of the parsed information.

This diff might be a bit easier to read with `-w`.

Signed-off-by: Martin Ågren <martin.agren@xxxxxxxxx>
---
 pretty.c | 69 ++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 42 insertions(+), 27 deletions(-)

diff --git a/pretty.c b/pretty.c
index c44ff87481..ddc7fd6aab 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1929,17 +1929,17 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */
 	return total_consumed;
 }
 
-static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
-				 const char *placeholder,
-				 struct format_commit_context *context)
+enum magic {
+	NO_MAGIC,
+	ADD_LF_BEFORE_NON_EMPTY,
+	DEL_LF_BEFORE_EMPTY,
+	ADD_SP_BEFORE_NON_EMPTY
+};
+
+/* 2 for 'bad magic', otherwise whether we consumed 0 or 1 chars. */
+static size_t parse_magic(const char *placeholder, enum magic *ret)
 {
-	size_t consumed, orig_len;
-	enum {
-		NO_MAGIC,
-		ADD_LF_BEFORE_NON_EMPTY,
-		DEL_LF_BEFORE_EMPTY,
-		ADD_SP_BEFORE_NON_EMPTY
-	} magic = NO_MAGIC;
+	enum magic magic;
 
 	switch (placeholder[0]) {
 	case '-':
@@ -1952,28 +1952,43 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
 		magic = ADD_SP_BEFORE_NON_EMPTY;
 		break;
 	default:
-		break;
+		*ret = NO_MAGIC;
+		return 0;
 	}
-	if (magic != NO_MAGIC) {
-		placeholder++;
 
-		switch (placeholder[0]) {
-		case 'w':
-			/*
-			 * `%+w()` cannot ever expand to a non-empty string,
-			 * and it potentially changes the layout of preceding
-			 * contents. We're thus not able to handle the magic in
-			 * this combination and refuse the pattern.
-			 */
-			return 0;
-		};
-	}
+	switch (placeholder[1]) {
+	case 'w':
+		/*
+		 * `%+w()` cannot ever expand to a non-empty string,
+		 * and it potentially changes the layout of preceding
+		 * contents. We're thus not able to handle the magic in
+		 * this combination and refuse the pattern.
+		 */
+		*ret = NO_MAGIC;
+		return 2;
+	};
+
+	*ret = magic;
+	return 1;
+}
+
+static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
+				 const char *placeholder,
+				 struct format_commit_context *context)
+{
+	size_t consumed, orig_len;
+	enum magic magic;
+
+	consumed = parse_magic(placeholder, &magic);
+	if (consumed > 1)
+		return 0;
+	placeholder += consumed;
 
 	orig_len = sb->len;
 	if (context->pad.flush_type == no_flush)
-		consumed = format_commit_one(sb, placeholder, context);
+		consumed += format_commit_one(sb, placeholder, context);
 	else
-		consumed = format_and_pad_commit(sb, placeholder, context);
+		consumed += format_and_pad_commit(sb, placeholder, context);
 	if (magic == NO_MAGIC)
 		return consumed;
 
@@ -1986,7 +2001,7 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */
 		else if (magic == ADD_SP_BEFORE_NON_EMPTY)
 			strbuf_insertstr(sb, orig_len, " ");
 	}
-	return consumed + 1;
+	return consumed;
 }
 
 void userformat_find_requirements(const char *fmt, struct userformat_want *w)
-- 
2.49.0.472.ge94155a9ec