Merge branch 'lt/diffgen' into next

* lt/diffgen:
  built-in diff: minimum tweaks
  builtin-diff: \No newline at end of file.
  Use a *real* built-in diff generator

diff.c

@@ -8,6 +8,7 @@
 #include "quote.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "xdiff/xdiff.h"
 
 static const char *diff_opts = "-pu";
 
@@ -178,6 +179,70 @@ static void emit_rewrite_diff(const char *name_a,
 		copy_file('+', temp[1].name);
 }
 
+static int fill_mmfile(mmfile_t *mf, const char *file)
+{
+	int fd = open(file, O_RDONLY);
+	struct stat st;
+	char *buf;
+	unsigned long size;
+
+	mf->ptr = NULL;
+	mf->size = 0;
+	if (fd < 0)
+		return 0;
+	fstat(fd, &st);
+	size = st.st_size;
+	buf = xmalloc(size);
+	mf->ptr = buf;
+	mf->size = size;
+	while (size) {
+		int retval = read(fd, buf, size);
+		if (retval < 0) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
+			break;
+		}
+		if (!retval)
+			break;
+		buf += retval;
+		size -= retval;
+	}
+	mf->size -= size;
+	close(fd);
+	return 0;
+}
+
+struct emit_callback {
+	const char **label_path;
+};
+
+static int fn_out(void *priv, mmbuffer_t *mb, int nbuf)
+{
+	int i;
+	struct emit_callback *ecbdata = priv;
+
+	if (ecbdata->label_path[0]) {
+		printf("--- %s\n", ecbdata->label_path[0]);
+		printf("+++ %s\n", ecbdata->label_path[1]);
+		ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
+	}
+	for (i = 0; i < nbuf; i++)
+		if (!fwrite(mb[i].ptr, mb[i].size, 1, stdout))
+			return -1;
+	return 0;
+}
+
+#define FIRST_FEW_BYTES 8000
+static int mmfile_is_binary(mmfile_t *mf)
+{
+	long sz = mf->size;
+	if (FIRST_FEW_BYTES < sz)
+		sz = FIRST_FEW_BYTES;
+	if (memchr(mf->ptr, 0, sz))
+		return 1;
+	return 0;
+}
+
 static const char *builtin_diff(const char *name_a,
 			 const char *name_b,
 			 struct diff_tempfile *temp,
@@ -186,6 +251,7 @@ static const char *builtin_diff(const char *name_a,
 			 const char **args)
 {
 	int i, next_at, cmd_size;
+	mmfile_t mf1, mf2;
 	const char *const diff_cmd = "diff -L%s -L%s";
 	const char *const diff_arg  = "-- %s %s||:"; /* "||:" is to return 0 */
 	const char *input_name_sq[2];
@@ -255,12 +321,44 @@ static const char *builtin_diff(const char *name_a,
 		}
 	}
 
-	/* This is disgusting */
-	*args++ = "sh";
-	*args++ = "-c";
-	*args++ = cmd;
-	*args = NULL;
-	return "/bin/sh";
+	/* Un-quote the paths */
+	if (label_path[0][0] != '/')
+		label_path[0] = quote_two("a/", name_a);
+	if (label_path[1][0] != '/')
+		label_path[1] = quote_two("b/", name_b);
+
+	if (fill_mmfile(&mf1, temp[0].name) < 0 ||
+	    fill_mmfile(&mf2, temp[1].name) < 0)
+		die("unable to read files to diff");
+
+	if (mmfile_is_binary(&mf1) || mmfile_is_binary(&mf2))
+		printf("Binary files %s and %s differ\n",
+		       label_path[0], label_path[1]);
+	else {
+		/* Crazy xdl interfaces.. */
+		const char *diffopts = getenv("GIT_DIFF_OPTS");
+		xpparam_t xpp;
+		xdemitconf_t xecfg;
+		xdemitcb_t ecb;
+		struct emit_callback ecbdata;
+
+		ecbdata.label_path = label_path;
+		xpp.flags = XDF_NEED_MINIMAL;
+		xecfg.ctxlen = 3;
+		if (!diffopts)
+			;
+		else if (!strncmp(diffopts, "--unified=", 10))
+			xecfg.ctxlen = strtoul(diffopts + 10, NULL, 10);
+		else if (!strncmp(diffopts, "-u", 2))
+			xecfg.ctxlen = strtoul(diffopts + 2, NULL, 10);
+		ecb.outf = fn_out;
+		ecb.priv = &ecbdata;
+		xdl_diff(&mf1, &mf2, &xpp, &xecfg, &ecb);
+	}
+
+	free(mf1.ptr);
+	free(mf2.ptr);
+	return NULL;
 }
 
 struct diff_filespec *alloc_filespec(const char *path)