Add builtin git-last-modified.

This is a plumbing command which can be used by gitweb. It will scan a list of commits and/or refs and return the time in seconds for the youngest commit. This value can then be used to generate and check the Last-Modified and Is-Modified-Since HTTP headers.

---

The following two commands lines are similar:

$ git for-each-ref --count=1 --sort=-committerdate '--format=%(committerdate)' refs/heads
$ git last-modified --branches

The last-modified version is a bit faster (5-10%).

I'm not 100% sure how this command and if this command should be used by gitweb. But I'll post the patch anyway for comments.

Robert

 .gitignore                          |    1 +
 Documentation/git-last-modified.txt |   49 ++++++++++++++++++++++++++++
 Makefile                            |    3 +-
 builtin-last-modified.c             |   61 +++++++++++++++++++++++++++++++++++
 builtin.h                           |    1 +
 git.c                               |    1 +
 t/t3810-last-modified.sh            |   57 ++++++++++++++++++++++++++++++++
 7 files changed, 172 insertions(+), 1 deletions(-)

index 2904f12..ffca6c5 100644
@@ -58,6 +58,7 @@ git-lost-found
 git-ls-files
 git-ls-remote
 git-ls-tree
+git-last-modified
 git-mailinfo
 git-mailsplit
 git-merge

index fa1a022..1f169ac 100644
@@ -312,7 +312,8 @@ BUILTIN_OBJS = \
 	builtin-verify-pack.o \
 	builtin-write-tree.o \
 	builtin-show-ref.o \
-	builtin-pack-refs.o
+	builtin-pack-refs.o \
+	builtin-last-modified.o
 
 GITLIBS = $(LIB_FILE) $(XDIFF_LIB)
 EXTLIBS = -lz

index df72d09..862cadb 100644
@@ -75,5 +75,6 @@ extern int cmd_write_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_verify_pack(int argc, const char **argv, const char *prefix);
 extern int cmd_show_ref(int argc, const char **argv, const char *prefix);
 extern int cmd_pack_refs(int argc, const char **argv, const char *prefix);
+extern int cmd_last_modified(int argc, const char **argv, const char *prefix);
 
 #endif

index c82ca45..e6242e6 100644
@@ -269,6 +269,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "verify-pack", cmd_verify_pack },
 		{ "show-ref", cmd_show_ref, RUN_SETUP },
 		{ "pack-refs", cmd_pack_refs, RUN_SETUP },
+		{ "last-modified", cmd_last_modified, RUN_SETUP },
 	};
 	int i;
 

1.5.0.rc0.g2708-dirty