[PATCH] Make "git diff" work inside relative subdirectories

We always show the diff as an absolute path, but pathnames to diff are
taken relative to the current working directory (and if no pathnames are
given, the default ends up being all of the current working directory).

Note that "../xyz" also works, so you can do

	cd linux/drivers/char
	git diff ../block

and it will generate a diff of the linux/drivers/block changes.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 110 insertions, 0 deletions

diff --git a/setup.c b/setup.c
new file mode 100644
index 0000000000..453bddbb17
--- /dev/null
+++ b/setup.c
@@ -0,0 +1,110 @@
+#include "cache.h"
+
+const char **get_pathspec(const char *prefix, char **pathspec)
+{
+	char *entry = *pathspec;
+	char **p;
+	int prefixlen;
+
+	if (!prefix) {
+		char **p;
+		if (!entry)
+			return NULL;
+		p = pathspec;
+		do {
+			if (*entry != '.')
+				continue;
+			/* fixup ? */
+		} while ((entry = *++p) != NULL);
+		return (const char **) pathspec;
+	}
+
+	if (!entry) {
+		static const char *spec[2];
+		spec[0] = prefix;
+		spec[1] = NULL;
+		return spec;
+	}
+
+	/* Otherwise we have to re-write the entries.. */
+	prefixlen = strlen(prefix);
+	p = pathspec;
+	do {
+		int speclen, len = prefixlen;
+		char *n;
+
+		for (;;) {
+			if (!strcmp(entry, ".")) {
+				entry++;
+				break;
+			}
+			if (!strncmp(entry, "./", 2)) {
+				entry += 2;
+				continue;
+			}
+			if (!strncmp(entry, "../", 3)) {
+				do {
+					if (!len)
+						die("'%s' is outside repository", *p);
+					len--;
+				} while (len && prefix[len-1] != '/');
+				entry += 3;
+				continue;
+			}
+			break;
+		}
+		speclen = strlen(entry);
+		n = xmalloc(speclen + len + 1);
+		
+		memcpy(n, prefix, len);
+		memcpy(n + len, entry, speclen+1);
+		*p = n;
+	} while ((entry = *++p) != NULL);
+	return (const char **) pathspec;
+}
+
+const char *setup_git_directory(void)
+{
+	static char cwd[PATH_MAX+1];
+	int len, offset;
+
+	/*
+	 * If GIT_DIR is set explicitly, we're not going
+	 * to do any discovery
+	 */
+	if (gitenv(GIT_DIR_ENVIRONMENT))
+		return NULL;
+
+	if (!getcwd(cwd, sizeof(cwd)) || cwd[0] != '/')
+		die("Unable to read current working directory");
+
+	offset = len = strlen(cwd);
+	for (;;) {
+		/*
+		 * We always want to see a .git/HEAD and a .git/refs/
+		 * subdirectory
+		 */
+		if (!access(".git/HEAD", R_OK) && !access(".git/refs/", X_OK)) {
+			/*
+			 * Then we need either a GIT_OBJECT_DIRECTORY define
+			 * or a .git/objects/ directory
+			 */
+			if (gitenv(DB_ENVIRONMENT) || !access(".git/objects/", X_OK))
+				break;
+		}
+		chdir("..");
+		do {
+			if (!offset)
+				die("Not a git repository");
+		} while (cwd[--offset] != '/');
+	}
+
+	if (offset == len)
+		return NULL;
+
+	/* Make "offset" point to past the '/', and add a '/' at the end */
+	offset++;
+	cwd[len++] = '/';
+	cwd[len] = 0;
+	return cwd + offset;
+}