xdiff-interface: provide a separate consume callback for hunks

The previous commit taught xdiff to optionally provide the hunk header
data to a specialized callback. But most users of xdiff actually use our
more convenient xdi_diff_outf() helper, which ensures that our callbacks
are always fed whole lines.

Let's plumb the special hunk-callback through this interface, too. It
will follow the same rule as xdiff when the hunk callback is NULL (i.e.,
continue to pass a stringified hunk header to the line callback). Since
we add NULL to each caller, there should be no behavior change yet.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

combine-diff.c

@@ -419,8 +419,8 @@ static void combine_diff(const struct object_id *parent, unsigned int mode,
 	state.num_parent = num_parent;
 	state.n = n;
 
-	if (xdi_diff_outf(&parent_file, result_file, consume_line, &state,
-			  &xpp, &xecfg))
+	if (xdi_diff_outf(&parent_file, result_file, NULL, consume_line,
+			  &state, &xpp, &xecfg))
 		die("unable to generate combined diff for %s",
 		    oid_to_hex(parent));
 	free(parent_file.ptr);

diff.c

@@ -2045,8 +2045,8 @@ static void diff_words_show(struct diff_words_data *diff_words)
 	xpp.flags = 0;
 	/* as only the hunk header will be parsed, we need a 0-context */
 	xecfg.ctxlen = 0;
-	if (xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
-			  &xpp, &xecfg))
+	if (xdi_diff_outf(&minus, &plus, NULL, fn_out_diff_words_aux,
+			  diff_words, &xpp, &xecfg))
 		die("unable to generate word diff");
 	free(minus.ptr);
 	free(plus.ptr);
@@ -3495,8 +3495,8 @@ static void builtin_diff(const char *name_a,
 			xecfg.ctxlen = strtoul(v, NULL, 10);
 		if (o->word_diff)
 			init_diff_words_data(&ecbdata, o, one, two);
-		if (xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
-				  &xpp, &xecfg))
+		if (xdi_diff_outf(&mf1, &mf2, NULL, fn_out_consume,
+				  &ecbdata, &xpp, &xecfg))
 			die("unable to generate diff for %s", one->path);
 		if (o->word_diff)
 			free_diff_words_data(&ecbdata);
@@ -3604,8 +3604,8 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		xpp.anchors_nr = o->anchors_nr;
 		xecfg.ctxlen = o->context;
 		xecfg.interhunkctxlen = o->interhunkcontext;
-		if (xdi_diff_outf(&mf1, &mf2, diffstat_consume, diffstat,
-				  &xpp, &xecfg))
+		if (xdi_diff_outf(&mf1, &mf2, NULL, diffstat_consume,
+				  diffstat, &xpp, &xecfg))
 			die("unable to generate diffstat for %s", one->path);
 	}
 
@@ -3652,8 +3652,8 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 		memset(&xecfg, 0, sizeof(xecfg));
 		xecfg.ctxlen = 1; /* at least one context line */
 		xpp.flags = 0;
-		if (xdi_diff_outf(&mf1, &mf2, checkdiff_consume, &data,
-				  &xpp, &xecfg))
+		if (xdi_diff_outf(&mf1, &mf2, NULL, checkdiff_consume,
+				  &data, &xpp, &xecfg))
 			die("unable to generate checkdiff for %s", one->path);
 
 		if (data.ws_rule & WS_BLANK_AT_EOF) {
@@ -5712,8 +5712,8 @@ static int diff_get_patch_id(struct diff_options *options, struct object_id *oid
 		xpp.flags = 0;
 		xecfg.ctxlen = 3;
 		xecfg.flags = 0;
-		if (xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
-				  &xpp, &xecfg))
+		if (xdi_diff_outf(&mf1, &mf2, NULL, patch_id_consume,
+				  &data, &xpp, &xecfg))
 			return error("unable to generate patch-id diff for %s",
 				     p->one->path);
 	}

diffcore-pickaxe.c

@@ -62,7 +62,7 @@ static int diff_grep(mmfile_t *one, mmfile_t *two,
 	ecbdata.hit = 0;
 	xecfg.ctxlen = o->context;
 	xecfg.interhunkctxlen = o->interhunkcontext;
-	if (xdi_diff_outf(one, two, diffgrep_consume, &ecbdata, &xpp, &xecfg))
+	if (xdi_diff_outf(one, two, NULL, diffgrep_consume, &ecbdata, &xpp, &xecfg))
 		return 0;
 	return ecbdata.hit;
 }

range-diff.c

@@ -190,7 +190,7 @@ static int diffsize(const char *a, const char *b)
 	mf2.size = strlen(b);
 
 	cfg.ctxlen = 3;
-	if (!xdi_diff_outf(&mf1, &mf2, diffsize_consume, &count, &pp, &cfg))
+	if (!xdi_diff_outf(&mf1, &mf2, NULL, diffsize_consume, &count, &pp, &cfg))
 		return count;
 
 	error(_("failed to generate diff"));

xdiff-interface.c

@@ -9,7 +9,8 @@
 #include "xdiff/xutils.h"
 
 struct xdiff_emit_state {
-	xdiff_emit_consume_fn consume;
+	xdiff_emit_hunk_fn hunk_fn;
+	xdiff_emit_line_fn line_fn;
 	void *consume_callback_data;
 	struct strbuf remainder;
 };
@@ -59,6 +60,22 @@ int parse_hunk_header(char *line, int len,
 	return -!!memcmp(cp, " @@", 3);
 }
 
+static int xdiff_out_hunk(void *priv_,
+			  long old_begin, long old_nr,
+			  long new_begin, long new_nr,
+			  const char *func, long funclen)
+{
+	struct xdiff_emit_state *priv = priv_;
+
+	if (priv->remainder.len)
+		BUG("xdiff emitted hunk in the middle of a line");
+
+	priv->hunk_fn(priv->consume_callback_data,
+		      old_begin, old_nr, new_begin, new_nr,
+		      func, funclen);
+	return 0;
+}
+
 static void consume_one(void *priv_, char *s, unsigned long size)
 {
 	struct xdiff_emit_state *priv = priv_;
@@ -67,7 +84,7 @@ static void consume_one(void *priv_, char *s, unsigned long size)
 		unsigned long this_size;
 		ep = memchr(s, '\n', size);
 		this_size = (ep == NULL) ? size : (ep - s + 1);
-		priv->consume(priv->consume_callback_data, s, this_size);
+		priv->line_fn(priv->consume_callback_data, s, this_size);
 		size -= this_size;
 		s += this_size;
 	}
@@ -141,7 +158,9 @@ int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t co
 }
 
 int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
-		  xdiff_emit_consume_fn fn, void *consume_callback_data,
+		  xdiff_emit_hunk_fn hunk_fn,
+		  xdiff_emit_line_fn line_fn,
+		  void *consume_callback_data,
 		  xpparam_t const *xpp, xdemitconf_t const *xecfg)
 {
 	int ret;
@@ -149,9 +168,12 @@ int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
 	xdemitcb_t ecb;
 
 	memset(&state, 0, sizeof(state));
-	state.consume = fn;
+	state.hunk_fn = hunk_fn;
+	state.line_fn = line_fn;
 	state.consume_callback_data = consume_callback_data;
 	memset(&ecb, 0, sizeof(ecb));
+	if (hunk_fn)
+		ecb.out_hunk = xdiff_out_hunk;
 	ecb.out_line = xdiff_outf;
 	ecb.priv = &state;
 	strbuf_init(&state.remainder, 0);

xdiff-interface.h

@@ -11,11 +11,17 @@
  */
 #define MAX_XDIFF_SIZE (1024UL * 1024 * 1023)
 
-typedef void (*xdiff_emit_consume_fn)(void *, char *, unsigned long);
+typedef void (*xdiff_emit_line_fn)(void *, char *, unsigned long);
+typedef void (*xdiff_emit_hunk_fn)(void *data,
+				   long old_begin, long old_nr,
+				   long new_begin, long new_nr,
+				   const char *func, long funclen);
 
 int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t const *xecfg, xdemitcb_t *ecb);
 int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
-		  xdiff_emit_consume_fn fn, void *consume_callback_data,
+		  xdiff_emit_hunk_fn hunk_fn,
+		  xdiff_emit_line_fn line_fn,
+		  void *consume_callback_data,
 		  xpparam_t const *xpp, xdemitconf_t const *xecfg);
 int parse_hunk_header(char *line, int len,
 		      int *ob, int *on,