pretty: add abbrev option to %(describe)

The %(describe) placeholder by default, like `git describe`, uses a
seven-character abbreviated commit object name. This may not be
sufficient to fully describe all commits in a given repository,
resulting in a placeholder replacement changing its length because the
repository grew in size.  This could cause the output of git-archive to
change.

Add the --abbrev option to `git describe` to the placeholder interface
in order to provide tools to the user for fine-tuning project defaults
and ensure reproducible archives.

One alternative would be to just always specify --abbrev=40 but this may
be a bit too biased...

Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/pretty.c b/pretty.c
index 52741fa0a9..d5a34eff91 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1220,10 +1220,12 @@ static size_t parse_describe_args(const char *start, struct strvec *args)
 		char *name;
 		enum {
 			DESCRIBE_ARG_BOOL,
+			DESCRIBE_ARG_INTEGER,
 			DESCRIBE_ARG_STRING,
 		} type;
 	}  option[] = {
 		{ "tags", DESCRIBE_ARG_BOOL},
+		{ "abbrev", DESCRIBE_ARG_INTEGER },
 		{ "exclude", DESCRIBE_ARG_STRING },
 		{ "match", DESCRIBE_ARG_STRING },
 	};
@@ -1247,6 +1249,19 @@ static size_t parse_describe_args(const char *start, struct strvec *args)
 					found = 1;
 				}
 				break;
+			case DESCRIBE_ARG_INTEGER:
+				if (match_placeholder_arg_value(arg, option[i].name, &arg,
+								&argval, &arglen)) {
+					char *endptr;
+					if (!arglen)
+						return 0;
+					strtol(argval, &endptr, 10);
+					if (endptr - argval != arglen)
+						return 0;
+					strvec_pushf(args, "--%s=%.*s", option[i].name, (int)arglen, argval);
+					found = 1;
+				}
+				break;
 			case DESCRIBE_ARG_STRING:
 				if (match_placeholder_arg_value(arg, option[i].name, &arg,
 								&argval, &arglen)) {