[PATCH v2 2/2] teach git-archive to auto detect the output format

[Dmitry Potapov <dpotapov@gmail.com>]

When I type something like this:
  git archive -o my-v2.0.zip v2.0
it is almost certainly that I want to create a zip archive, and not
a tar file.

This patch teaches git-archive to auto detect the output format from the
file name. Currently, only '.zip' is supported. If the auto detect failed,
the tar format is used as before. The auto detect is not used when the
output format is specified explicitly.

Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
---

I have corrected all remarks except this:

On Sun, Sep 13, 2009 at 11:52:56AM -0700, Junio C Hamano wrote:
> > +		sprintf(fmt_opt, "--format=%s", format);
> > +		argv[argc++] = fmt_opt;
> > +		argv[argc] = NULL;
> 
> Did you make sure you are allowed to write into argv[] and the array is
> large enough?  You probably need to make a copy of the array.

Either --output or --format option was used before, and this option is
extracted from argv[] by parse_options(). So it should be space for at
least one argument in argv.


 Documentation/git-archive.txt |   13 +++++++++++--
 builtin-archive.c             |   25 ++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-archive.txt b/Documentation/git-archive.txt
index 1917f2e..3d1c1e7 100644
--- a/Documentation/git-archive.txt
+++ b/Documentation/git-archive.txt
@@ -34,8 +34,11 @@ OPTIONS
 -------
 
 --format=<fmt>::
-	Format of the resulting archive: 'tar' or 'zip'.  The default
-	is 'tar'.
+	Format of the resulting archive: 'tar' or 'zip'. If this option
+	is not given, and the output file is specified, the format is
+	inferred from the filename if possible (e.g. writing to "foo.zip"
+	makes the output to be in the zip format). Otherwise the output
+	format is `tar`.
 
 -l::
 --list::
@@ -130,6 +133,12 @@ git archive --format=zip --prefix=git-docs/ HEAD:Documentation/ > git-1.4.0-docs
 	Put everything in the current head's Documentation/ directory
 	into 'git-1.4.0-docs.zip', with the prefix 'git-docs/'.
 
+git archive -o latest.zip HEAD::
+
+	Create a Zip archive that contains the contents of the latest
+	commit on the current branch. Note that the output format is
+	inferred by the extension of the output file.
+
 
 SEE ALSO
 --------
diff --git a/builtin-archive.c b/builtin-archive.c
index 565314b..6efba6f 100644
--- a/builtin-archive.c
+++ b/builtin-archive.c
@@ -60,6 +60,17 @@ static int run_remote_archiver(int argc, const char **argv,
 	return !!rv;
 }
 
+static const char* format_from_name(const char *filename)
+{
+	const char *ext = strrchr(filename, '.');
+	if (!ext)
+		return NULL;
+	ext++;
+	if (!strcasecmp(ext, "zip"))
+		return "zip";
+	return NULL;
+}
+
 #define PARSE_OPT_KEEP_ALL ( PARSE_OPT_KEEP_DASHDASH | 	\
 			     PARSE_OPT_KEEP_ARGV0 | 	\
 			     PARSE_OPT_KEEP_UNKNOWN |	\
@@ -70,6 +81,7 @@ int cmd_archive(int argc, const char **argv, const char *prefix)
 	const char *exec = "git-upload-archive";
 	const char *output = NULL;
 	const char *remote = NULL;
+	const char *format = NULL;
 	struct option local_opts[] = {
 		OPT_STRING('o', "output", &output, "file",
 			"write the archive to this file"),
@@ -77,14 +89,25 @@ int cmd_archive(int argc, const char **argv, const char *prefix)
 			"retrieve the archive from remote repository <repo>"),
 		OPT_STRING(0, "exec", &exec, "cmd",
 			"path to the remote git-upload-archive command"),
+		OPT_STRING(0, "format", &format, "fmt", "archive format"),
 		OPT_END()
 	};
+	char fmt_opt[32];
 
 	argc = parse_options(argc, argv, prefix, local_opts, NULL,
 			     PARSE_OPT_KEEP_ALL);
 
-	if (output)
+	if (output) {
 		create_output_file(output);
+		if (!format)
+			format = format_from_name(output);
+	}
+
+	if (format) {
+		sprintf(fmt_opt, "--format=%s", format);
+		argv[argc++] = fmt_opt;
+		argv[argc] = NULL;
+	}
 
 	if (remote)
 		return run_remote_archiver(argc, argv, remote, exec);
-- 
1.6.5.rc1.2.g6bb993