builtin-diff: call it "git-diff", really.

Call it "git diff" not "git diffn", remove the shell script
version, and hardlink the git binary to it.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -115,7 +115,7 @@ SPARSE_FLAGS = -D__BIG_ENDIAN__ -D__powerpc__
 SCRIPT_SH = \
 	git-add.sh git-bisect.sh git-branch.sh git-checkout.sh \
 	git-cherry.sh git-clean.sh git-clone.sh git-commit.sh \
-	git-count-objects.sh git-diff.sh git-fetch.sh \
+	git-count-objects.sh git-fetch.sh \
 	git-format-patch.sh git-ls-remote.sh \
 	git-merge-one-file.sh git-parse-remote.sh \
 	git-prune.sh git-pull.sh git-push.sh git-rebase.sh \
@@ -167,7 +167,8 @@ PROGRAMS = \
 	git-name-rev$X git-pack-redundant$X git-repo-config$X git-var$X \
 	git-describe$X git-merge-tree$X git-blame$X git-imap-send$X
 
-BUILT_INS = git-log$X
+BUILT_INS = git-log$X \
+	git-diff$X
 
 # what 'all' will build and 'install' will install, in gitexecdir
 ALL_PROGRAMS = $(PROGRAMS) $(SIMPLE_PROGRAMS) $(SCRIPTS)

git.c

@@ -46,7 +46,7 @@ static void handle_internal_command(int argc, const char **argv, char **envp)
 		{ "log", cmd_log },
 		{ "whatchanged", cmd_whatchanged },
 		{ "show", cmd_show },
-		{ "diffn", cmd_diff },
+		{ "diff", cmd_diff },
 	};
 	int i;