[PATCH] Reworked external diff interface.

This introduces three public functions for diff-cache and friends can
use to call out to the GIT_EXTERNAL_DIFF program when they wish to.

A normal "add/remove/change" entry is turned into 7-parameter process
invocation of GIT_EXTERNAL_DIFF program as before.  In addition, the
program can now be called with a single parameter when diff-cache and
friends want to report an unmerged path. 

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

diff.c

@@ -194,13 +194,15 @@ void run_external_diff(const char *name,
 	int pid, status;
 	static int atexit_asked = 0;
 
-	prepare_temp_file(name, &temp[0], one);
-	prepare_temp_file(name, &temp[1], two);
-	if (! atexit_asked &&
-	    (temp[0].name == temp[0].tmp_path ||
-	     temp[1].name == temp[1].tmp_path)) {
-		atexit_asked = 1;
-		atexit(remove_tempfile);
+	if (one && two) {
+		prepare_temp_file(name, &temp[0], one);
+		prepare_temp_file(name, &temp[1], two);
+		if (! atexit_asked &&
+		    (temp[0].name == temp[0].tmp_path ||
+		     temp[1].name == temp[1].tmp_path)) {
+			atexit_asked = 1;
+			atexit(remove_tempfile);
+		}
 	}
 
 	fflush(NULL);
@@ -209,16 +211,23 @@ void run_external_diff(const char *name,
 		die("unable to fork");
 	if (!pid) {
 		const char *pgm = external_diff();
-		if (pgm)
-			execlp(pgm, pgm,
-			       name,
-			       temp[0].name, temp[0].hex, temp[0].mode,
-			       temp[1].name, temp[1].hex, temp[1].mode,
-			       NULL);
+		if (pgm) {
+			if (one && two)
+				execlp(pgm, pgm,
+				       name,
+				       temp[0].name, temp[0].hex, temp[0].mode,
+				       temp[1].name, temp[1].hex, temp[1].mode,
+				       NULL);
+			else
+				execlp(pgm, pgm, name, NULL);
+		}
 		/*
 		 * otherwise we use the built-in one.
 		 */
-		builtin_diff(name, temp);
+		if (one && two)
+			builtin_diff(name, temp);
+		else
+			printf("* Unmerged path %s\n", name);
 		exit(0);
 	}
 	if (waitpid(pid, &status, 0) < 0 || !WIFEXITED(status))
@@ -227,41 +236,55 @@ void run_external_diff(const char *name,
 	remove_tempfile();
 }
 
-void show_diff_empty(const struct cache_entry *ce, int reverse)
+void diff_addremove(int addremove, unsigned mode,
+		    const unsigned char *sha1,
+		    const char *base, const char *path)
 {
+	char concatpath[PATH_MAX];
 	struct diff_spec spec[2], *one, *two;
 
-	memcpy(spec[0].u.sha1, ce->sha1, 20);
-	spec[0].mode = ntohl(ce->ce_mode);
+	memcpy(spec[0].u.sha1, sha1, 20);
+	spec[0].mode = mode;
 	spec[0].sha1_valid = spec[0].file_valid = 1;
 	spec[1].file_valid = 0;
 
-	if (reverse) {
+	if (addremove == '+') {
 		one = spec + 1; two = spec;
 	} else {
 		one = spec; two = one + 1;
 	}
-
-	run_external_diff(ce->name, one, two);
+
+	if (path) {
+		strcpy(concatpath, base);
+		strcat(concatpath, "/");
+		strcat(concatpath, path);
+	}
+	run_external_diff(path ? concatpath : base, one, two);
 }
 
-void show_differences(const struct cache_entry *ce, int reverse) 
-{
-	struct diff_spec spec[2], *one, *two;
-
-	memcpy(spec[0].u.sha1, ce->sha1, 20);
-	spec[0].mode = ntohl(ce->ce_mode);
+void diff_change(unsigned old_mode, unsigned new_mode,
+		 const unsigned char *old_sha1,
+		 const unsigned char *new_sha1,
+		 const char *base, const char *path) {
+	char concatpath[PATH_MAX];
+	struct diff_spec spec[2];
+
+	memcpy(spec[0].u.sha1, old_sha1, 20);
+	spec[0].mode = old_mode;
+	memcpy(spec[1].u.sha1, new_sha1, 20);
+	spec[1].mode = new_mode;
 	spec[0].sha1_valid = spec[0].file_valid = 1;
+	spec[1].sha1_valid = spec[1].file_valid = 1;
 
-	spec[1].u.name = ce->name; /* the name we stated */
-	spec[1].sha1_valid = 0;
-	spec[1].file_valid = 1;
-
-	if (reverse) {
-		one = spec + 1; two = spec;
-	} else {
-		one = spec; two = one + 1;
+	if (path) {
+		strcpy(concatpath, base);
+		strcat(concatpath, "/");
+		strcat(concatpath, path);
 	}
+	run_external_diff(path ? concatpath : base, &spec[0], &spec[1]);
+}
 
-	run_external_diff(ce->name, one, two);
+void diff_unmerge(const char *path)
+{
+	run_external_diff(path, NULL, NULL);
 }

diff.h

@@ -4,11 +4,20 @@
 #ifndef DIFF_H
 #define DIFF_H
 
-/* These two are for backward compatibility with show-diff;
- * new users should not use them.
- */
-extern void show_differences(const struct cache_entry *ce, int reverse);
-extern void show_diff_empty(const struct cache_entry *ce, int reverse);
+extern void diff_addremove(int addremove,
+			   unsigned mode,
+			   const unsigned char *sha1,
+			   const char *base,
+			   const char *path);
+
+extern void diff_change(unsigned mode1, unsigned mode2,
+			     const unsigned char *sha1,
+			     const unsigned char *sha2,
+			     const char *base, const char *path);
+
+extern void diff_unmerge(const char *path);
+
+/* These are for diff-tree-helper */
 
 struct diff_spec {
 	union {