[PATCH] pretty-format: add append line-feed format specifier

[Harry Jeffery <harry@exec64.co.uk>]

Add a new format prefix `_` that causes a line-feed to be inserted
immediately after an expansion if the expansion expands to a non-empty
string. This is useful for when you would like a line for an expansion
to be prepended, but only when the expansion expands to a non empty
string, such as inserting a '%_d' expansion before a commit to show any
refs pointing towards it.

Signed-off-by: Harry Jeffery <harry@exec64.co.uk>
---
  Documentation/pretty-formats.txt |  4 ++++
  pretty.c                         | 10 ++++++++--
  2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/Documentation/pretty-formats.txt 
b/Documentation/pretty-formats.txt
index 85d6353..842cd17 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -197,6 +197,10 @@ If you add a ` ` (space) after '%' of a 
placeholder, a space
  is inserted immediately before the expansion if and only if the
  placeholder expands to a non-empty string.

+If you add a `_` (underscore) after '%' of a placeholder, a line-feed
+is inserted immediately after the expansion if and only if the
+placeholder expands to a non-empty string.
+
  * 'tformat:'
  +
  The 'tformat:' format works exactly like 'format:', except that it
diff --git a/pretty.c b/pretty.c
index 44b9f64..ddb930d 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1416,7 +1416,8 @@ static size_t format_commit_item(struct strbuf 
*sb, /* in UTF-8 */
  		NO_MAGIC,
  		ADD_LF_BEFORE_NON_EMPTY,
  		DEL_LF_BEFORE_EMPTY,
-		ADD_SP_BEFORE_NON_EMPTY
+		ADD_SP_BEFORE_NON_EMPTY,
+		ADD_LF_AFTER_NON_EMPTY
  	} magic = NO_MAGIC;

  	switch (placeholder[0]) {
@@ -1429,6 +1430,9 @@ static size_t format_commit_item(struct strbuf 
*sb, /* in UTF-8 */
  	case ' ':
  		magic = ADD_SP_BEFORE_NON_EMPTY;
  		break;
+	case '_':
+		magic = ADD_LF_AFTER_NON_EMPTY;
+		break;
  	default:
  		break;
  	}
@@ -1449,6 +1453,8 @@ static size_t format_commit_item(struct strbuf 
*sb, /* in UTF-8 */
  	} else if (orig_len != sb->len) {
  		if (magic == ADD_LF_BEFORE_NON_EMPTY)
  			strbuf_insert(sb, orig_len, "\n", 1);
+		else if (magic == ADD_LF_AFTER_NON_EMPTY)
+			strbuf_addch(sb, '\n');
  		else if (magic == ADD_SP_BEFORE_NON_EMPTY)
  			strbuf_insert(sb, orig_len, " ", 1);
  	}
@@ -1460,7 +1466,7 @@ static size_t userformat_want_item(struct strbuf 
*sb, const char *placeholder,
  {
  	struct userformat_want *w = context;

-	if (*placeholder == '+' || *placeholder == '-' || *placeholder == ' ')
+	if (*placeholder == '+' || *placeholder == '-' || *placeholder == ' ' 
|| *placeholder == '_')
  		placeholder++;

  	switch (*placeholder) {
-- 
2.1.0