[PATCH] Allow aliases to expand to shell commands

[Theodore Ts'o <tytso@mit.edu>]

If the alias expansion is prefixed with an exclamation point, treat
it as a shell command which is run using system(3).

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
 Documentation/config.txt |    6 ++++++
 git.c                    |   10 ++++++++++
 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 4e650af..de185d8 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -222,6 +222,12 @@ alias.*::
 	spaces, the usual shell quoting and escaping is supported.
 	quote pair and a backslash can be used to quote them.
 
+	If the alias expansion is prefixed with an exclamation point,
+	it will be treated as a shell command.  For example, defining
+	"alias.new = !gitk --all --not ORIG_HEAD", the invocation 
+	"git new" is eqvuialent to running the shell command 
+	"gitk --all --not ORIG_HEAD".
+
 apply.whitespace::
 	Tells `git-apply` how to handle whitespaces, in the same way
 	as the '--whitespace' option. See gitlink:git-apply[1].
diff --git a/git.c b/git.c
index c43d4ff..fc08396 100644
--- a/git.c
+++ b/git.c
@@ -159,6 +159,16 @@ static int handle_alias(int *argcp, const char ***argv)
 	alias_command = (*argv)[0];
 	git_config(git_alias_config);
 	if (alias_string) {
+		if (alias_string[0] == '!') {
+			trace_printf("trace: alias to shell cmd: %s => %s\n",
+				     alias_command, alias_string+1);
+			ret = system(alias_string+1);
+			if (ret >= 0 && WIFEXITED(ret) && 
+			    WEXITSTATUS(ret) != 127)
+				exit(WEXITSTATUS(ret));
+			die("Failed to run '%s' when expanding alias '%s'\n", 
+			    alias_string, alias_command);
+		}
 		count = split_cmdline(alias_string, &new_argv);
 		option_count = handle_options(&new_argv, &count);
 		memmove(new_argv - option_count, new_argv,
-- 
1.5.0.rc4