Add "get_sha1()" helper function.

This allows the programs to use various simplified versions of
the SHA1 names, eg just say "HEAD" for the SHA1 pointed to by
the .git/HEAD file etc.

For example, this commit has been done with

	git-commit-tree $(git-write-tree) -p HEAD

instead of the traditional "$(cat .git/HEAD)" syntax.

16 files changed, 46 insertions, 16 deletions

diff --git a/cache.h b/cache.h
index af6345820..940ced031 100644
--- a/cache.h
+++ b/cache.h
@@ -146,6 +146,7 @@ extern int write_sha1_from_fd(const unsigned char *sha1, int fd);
 extern int has_sha1_file(const unsigned char *sha1);
 
 /* Convert to/from hex/sha1 representation */
+extern int get_sha1(const char *str, unsigned char *sha1);
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 
diff --git a/cat-file.c b/cat-file.c
index 3c47d79a1..d253ff938 100644
--- a/cat-file.c
+++ b/cat-file.c
@@ -12,7 +12,7 @@ int main(int argc, char **argv)
 	void *buf;
 	unsigned long size;
 
-	if (argc != 3 || get_sha1_hex(argv[2], sha1))
+	if (argc != 3 || get_sha1(argv[2], sha1))
 		usage("cat-file [-t | tagname] <sha1>");
 	buf = read_sha1_file(sha1, type, &size);
 	if (!buf)
diff --git a/commit-tree.c b/commit-tree.c
index 0c568d017..cfd6730fe 100644
--- a/commit-tree.c
+++ b/commit-tree.c
@@ -123,7 +123,7 @@ int main(int argc, char **argv)
 	for (i = 2; i < argc; i += 2) {
 		char *a, *b;
 		a = argv[i]; b = argv[i+1];
-		if (!b || strcmp(a, "-p") || get_sha1_hex(b, parent_sha1[parents]))
+		if (!b || strcmp(a, "-p") || get_sha1(b, parent_sha1[parents]))
 			usage(commit_tree_usage);
 		check_valid(parent_sha1[parents], "commit");
 		parents++;
diff --git a/convert-cache.c b/convert-cache.c
index 631d1aa91..4d34d2d57 100644
--- a/convert-cache.c
+++ b/convert-cache.c
@@ -303,7 +303,7 @@ int main(int argc, char **argv)
 	unsigned char sha1[20];
 	struct entry *entry;
 
-	if (argc != 2 || get_sha1_hex(argv[1], sha1))
+	if (argc != 2 || get_sha1(argv[1], sha1))
 		usage("convert-cache <sha1>");
 
 	entry = convert_entry(sha1);
diff --git a/diff-cache.c b/diff-cache.c
index 899e37361..03dd69df3 100644
--- a/diff-cache.c
+++ b/diff-cache.c
@@ -175,7 +175,7 @@ int main(int argc, char **argv)
 		usage(diff_cache_usage);
 	}
 
-	if (argc != 2 || get_sha1_hex(argv[1], tree_sha1))
+	if (argc != 2 || get_sha1(argv[1], tree_sha1))
 		usage(diff_cache_usage);
 
 	mark_merge_entries();
diff --git a/diff-tree.c b/diff-tree.c
index e7a5b7cc7..1186c5ce6 100644
--- a/diff-tree.c
+++ b/diff-tree.c
@@ -279,7 +279,7 @@ int main(int argc, char **argv)
 		usage(diff_tree_usage);
 	}
 
-	if (argc < 3 || get_sha1_hex(argv[1], old) || get_sha1_hex(argv[2], new))
+	if (argc < 3 || get_sha1(argv[1], old) || get_sha1(argv[2], new))
 		usage(diff_tree_usage);
 
 	if (argc > 3) {
diff --git a/export.c b/export.c
index 885f4e88f..78bfe9f22 100644
--- a/export.c
+++ b/export.c
@@ -73,8 +73,8 @@ int main(int argc, char **argv)
 	unsigned char top_sha1[20];
 
 	if (argc < 2 || argc > 4 ||
-	    get_sha1_hex(argv[1], top_sha1) ||
-	    (argc == 3 && get_sha1_hex(argv[2], base_sha1)))
+	    get_sha1(argv[1], top_sha1) ||
+	    (argc == 3 && get_sha1(argv[2], base_sha1)))
 		usage("git-export top [base]");
 	export(get_commit(top_sha1), argc==3 ? get_commit(base_sha1) : NULL);
 	return 0;
diff --git a/fsck-cache.c b/fsck-cache.c
index d8d2e594f..fbcd2b64f 100644
--- a/fsck-cache.c
+++ b/fsck-cache.c
@@ -178,7 +178,7 @@ int main(int argc, char **argv)
 		if (*arg == '-')
 			continue;
 
-		if (!get_sha1_hex(arg, head_sha1)) {
+		if (!get_sha1(arg, head_sha1)) {
 			struct commit *commit = lookup_commit(head_sha1);
 			struct object *obj;
 
diff --git a/ls-tree.c b/ls-tree.c
index d2ab02e34..339ac36a4 100644
--- a/ls-tree.c
+++ b/ls-tree.c
@@ -102,7 +102,7 @@ int main(int argc, char **argv)
 
 	if (argc != 2)
 		usage(ls_tree_usage);
-	if (get_sha1_hex(argv[1], sha1) < 0)
+	if (get_sha1(argv[1], sha1) < 0)
 		usage(ls_tree_usage);
 	sha1_file_directory = getenv(DB_ENVIRONMENT);
 	if (!sha1_file_directory)
diff --git a/merge-base.c b/merge-base.c
index 2c4088130..2ea44970d 100644
--- a/merge-base.c
+++ b/merge-base.c
@@ -58,8 +58,8 @@ int main(int argc, char **argv)
 	unsigned char rev1key[20], rev2key[20];
 
 	if (argc != 3 ||
-	    get_sha1_hex(argv[1], rev1key) ||
-	    get_sha1_hex(argv[2], rev2key)) {
+	    get_sha1(argv[1], rev1key) ||
+	    get_sha1(argv[2], rev2key)) {
 		usage("merge-base <commit-id> <commit-id>");
 	}
 	rev1 = lookup_commit(rev1key);
diff --git a/read-tree.c b/read-tree.c
index 604884a98..f8dc509a1 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -191,7 +191,7 @@ int main(int argc, char **argv)
 			merge = 1;
 			continue;
 		}
-		if (get_sha1_hex(arg, sha1) < 0)
+		if (get_sha1(arg, sha1) < 0)
 			usage(read_tree_usage);
 		if (stage > 3)
 			usage(read_tree_usage);
diff --git a/rev-list.c b/rev-list.c
index 77bfc29db..42fd154fc 100644
--- a/rev-list.c
+++ b/rev-list.c
@@ -7,7 +7,7 @@ int main(int argc, char **argv)
 	struct commit_list *list = NULL;
 	struct commit *commit;
 
-	if (argc != 2 || get_sha1_hex(argv[1], sha1))
+	if (argc != 2 || get_sha1(argv[1], sha1))
 		usage("rev-list <commit-id>");
 
 	commit = lookup_commit(sha1);
diff --git a/rev-tree.c b/rev-tree.c
index 95ec274fc..bfc8b1257 100644
--- a/rev-tree.c
+++ b/rev-tree.c
@@ -97,7 +97,7 @@ int main(int argc, char **argv)
 			arg++;
 			basemask |= 1<<nr;
 		}
-		if (nr >= MAX_COMMITS || get_sha1_hex(arg, sha1[nr]))
+		if (nr >= MAX_COMMITS || get_sha1(arg, sha1[nr]))
 			usage("rev-tree [--edges] [--cache <cache-file>] <commit-id> [<commit-id>]");
 		process_commit(sha1[nr]);
 		nr++;
diff --git a/sha1_file.c b/sha1_file.c
index 29f48d56b..d91e072f3 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -45,6 +45,35 @@ int get_sha1_hex(const char *hex, unsigned char *sha1)
 	return 0;
 }
 
+int get_sha1_file(const char *path, unsigned char *result)
+{
+	char buffer[60];
+	int fd = open(path, O_RDONLY);
+	int len;
+
+	if (fd < 0)
+		return -1;
+	len = read(fd, buffer, sizeof(buffer));
+	close(fd);
+	if (len < 40)
+		return -1;
+	return get_sha1_hex(buffer, result);
+}
+
+int get_sha1(const char *str, unsigned char *sha1)
+{
+	static char pathname[PATH_MAX];
+
+	if (!get_sha1_hex(str, sha1))
+		return 0;
+	if (!get_sha1_file(str, sha1))
+		return 0;
+	snprintf(pathname, sizeof(pathname), ".git/%s", str);
+	if (!get_sha1_file(pathname, sha1))
+		return 0;
+	return -1;
+}
+
 char * sha1_to_hex(const unsigned char *sha1)
 {
 	static char buffer[50];
diff --git a/tar-tree.c b/tar-tree.c
index ea7ea91ad..2c64f690e 100644
--- a/tar-tree.c
+++ b/tar-tree.c
@@ -338,7 +338,7 @@ int main(int argc, char **argv)
 		basedir = argv[2];
 		/* FALLTHROUGH */
 	case 2:
-		if (get_sha1_hex(argv[1], sha1) < 0)
+		if (get_sha1(argv[1], sha1) < 0)
 			usage(tar_tree_usage);
 		break;
 	default:
diff --git a/unpack-file.c b/unpack-file.c
index 6ff3d51c1..b7988c557 100644
--- a/unpack-file.c
+++ b/unpack-file.c
@@ -26,7 +26,7 @@ int main(int argc, char **argv)
 {
 	unsigned char sha1[20];
 
-	if (argc != 2 || get_sha1_hex(argv[1], sha1))
+	if (argc != 2 || get_sha1(argv[1], sha1))
 		usage("unpack-file.c <sha1>");
 
 	puts(create_temp_file(sha1));