Pretty-format: %[+-]x to tweak inter-item newlines

This teaches the "pretty" machinery to expand '%+x' to a LF followed by
the expansion of '%x' if and only if '%x' expands to a non-empty string,
and to remove LFs before '%-x' if '%x' expands to an empty string.  This
works for any supported expansion placeholder 'x'.

This is expected to be immediately useful to reproduce the commit log
message with "%s%+b%n"; "%s%n%b%n" adds one extra LF if the log message is
a one-liner.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 2a845b1e57590a6f18f05fd3efa858b736c1071a..ca9c6d1f8078900f3f08b24cd47ba802c5e80ba1 100644 (file)
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -132,6 +132,14 @@ The placeholders are:
 - '%n': newline
 - '%x00': print a byte from a hex code
 
+If you add a `{plus}` (plus sign) after '%' of a placeholder, a line-feed
+is inserted immediately before the expansion if and only if the
+placeholder expands to a non-empty string.
+
+If you add a `-` (minus sign) after '%' of a placeholder, line-feeds that
+immediately precede the expansion are deleted if and only if the
+placeholder expands to an empty string.
+
 * 'tformat:'
 +
 The 'tformat:' format works exactly like 'format:', except that it

diff --git a/pretty.c b/pretty.c
index f5983f8baa98b69338707b4220e64012ef4e5d11..081feb66026a473060a7beaf40de2618b792ac0f 100644 (file)
--- a/pretty.c
+++ b/pretty.c
@@ -595,8 +595,8 @@ static void format_decoration(struct strbuf *sb, const struct commit *commit)
                strbuf_addch(sb, ')');
 }
 
-static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
-                               void *context)
+static size_t format_commit_one(struct strbuf *sb, const char *placeholder,
+                               void *context)
 {
        struct format_commit_context *c = context;
        const struct commit *commit = c->commit;
@@ -739,6 +739,44 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
        return 0;       /* unknown placeholder */
 }
 
+static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
+                                void *context)
+{
+       int consumed;
+       size_t orig_len;
+       enum {
+               NO_MAGIC,
+               ADD_LF_BEFORE_NON_EMPTY,
+               DEL_LF_BEFORE_EMPTY,
+       } magic = NO_MAGIC;
+
+       switch (placeholder[0]) {
+       case '-':
+               magic = DEL_LF_BEFORE_EMPTY;
+               break;
+       case '+':
+               magic = ADD_LF_BEFORE_NON_EMPTY;
+               break;
+       default:
+               break;
+       }
+       if (magic != NO_MAGIC)
+               placeholder++;
+
+       orig_len = sb->len;
+       consumed = format_commit_one(sb, placeholder, context);
+       if (magic == NO_MAGIC)
+               return consumed;
+
+       if ((orig_len == sb->len) && magic == DEL_LF_BEFORE_EMPTY) {
+               while (sb->len && sb->buf[sb->len - 1] == '\n')
+                       strbuf_setlen(sb, sb->len - 1);
+       } else if ((orig_len != sb->len) && magic == ADD_LF_BEFORE_NON_EMPTY) {
+               strbuf_insert(sb, orig_len, "\n", 1);
+       }
+       return consumed + 1;
+}
+
 void format_commit_message(const struct commit *commit,
                           const void *format, struct strbuf *sb,
                           enum date_mode dmode)

diff --git a/t/t6006-rev-list-format.sh b/t/t6006-rev-list-format.sh
index 59d1f6283bec5cf7740d988dfd090c1463389c71..18a77a739ed326ab9cc17ca3838b3859becddabe 100755 (executable)
--- a/t/t6006-rev-list-format.sh
+++ b/t/t6006-rev-list-format.sh
@@ -162,4 +162,26 @@ test_expect_success 'empty email' '
        }
 '
 
+test_expect_success 'del LF before empty (1)' '
+       git show -s --pretty=format:"%s%n%-b%nThanks%n" HEAD^^ >actual &&
+       test $(wc -l <actual) = 2
+'
+
+test_expect_success 'del LF before empty (2)' '
+       git show -s --pretty=format:"%s%n%-b%nThanks%n" HEAD >actual &&
+       test $(wc -l <actual) = 6 &&
+       grep "^$" actual
+'
+
+test_expect_success 'add LF before non-empty (1)' '
+       git show -s --pretty=format:"%s%+b%nThanks%n" HEAD^^ >actual &&
+       test $(wc -l <actual) = 2
+'
+
+test_expect_success 'add LF before non-empty (2)' '
+       git show -s --pretty=format:"%s%+b%nThanks%n" HEAD >actual &&
+       test $(wc -l <actual) = 6 &&
+       grep "^$" actual
+'
+
 test_done