Merge branch 'rs/diff-whole-function'

* rs/diff-whole-function:
  diff: add option to show whole functions as context
  xdiff: factor out get_func_line()

Documentation/diff-options.txt

@@ -408,6 +408,10 @@ endif::git-format-patch[]
 	Show the context between diff hunks, up to the specified number
 	of lines, thereby fusing hunks that are close to each other.
 
+-W::
+--function-context::
+	Show whole surrounding functions of changes.
+
 ifndef::git-format-patch[]
 --exit-code::
 	Make the program exit with codes similar to diff(1).

diff.c

@@ -2169,6 +2169,8 @@ static void builtin_diff(const char *name_a,
 		xecfg.ctxlen = o->context;
 		xecfg.interhunkctxlen = o->interhunkcontext;
 		xecfg.flags = XDL_EMIT_FUNCNAMES;
+		if (DIFF_OPT_TST(o, FUNCCONTEXT))
+			xecfg.flags |= XDL_EMIT_FUNCCONTEXT;
 		if (pe)
 			xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
 		if (!diffopts)
@@ -3536,6 +3538,12 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (opt_arg(arg, '\0', "inter-hunk-context",
 			 &options->interhunkcontext))
 		;
+	else if (!strcmp(arg, "-W"))
+		DIFF_OPT_SET(options, FUNCCONTEXT);
+	else if (!strcmp(arg, "--function-context"))
+		DIFF_OPT_SET(options, FUNCCONTEXT);
+	else if (!strcmp(arg, "--no-function-context"))
+		DIFF_OPT_CLR(options, FUNCCONTEXT);
 	else if ((argcount = parse_long_opt("output", av, &optarg))) {
 		options->file = fopen(optarg, "w");
 		if (!options->file)

diff.h

@@ -79,6 +79,7 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_IGNORE_DIRTY_SUBMODULES (1 << 26)
 #define DIFF_OPT_OVERRIDE_SUBMODULE_CONFIG (1 << 27)
 #define DIFF_OPT_DIRSTAT_BY_LINE     (1 << 28)
+#define DIFF_OPT_FUNCCONTEXT         (1 << 29)
 
 #define DIFF_OPT_TST(opts, flag)    ((opts)->flags & DIFF_OPT_##flag)
 #define DIFF_OPT_SET(opts, flag)    ((opts)->flags |= DIFF_OPT_##flag)

t/t4051-diff-function-context.sh

@@ -0,0 +1,92 @@
+#!/bin/sh
+
+test_description='diff function context'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/diff-lib.sh
+
+
+cat <<\EOF >hello.c
+#include <stdio.h>
+
+static int a(void)
+{
+	/*
+	 * Dummy.
+	 */
+}
+
+static int hello_world(void)
+{
+	/* Classic. */
+	printf("Hello world.\n");
+
+	/* Success! */
+	return 0;
+}
+static int b(void)
+{
+	/*
+	 * Dummy, too.
+	 */
+}
+
+int main(int argc, char **argv)
+{
+	a();
+	b();
+	return hello_world();
+}
+EOF
+
+test_expect_success 'setup' '
+	git add hello.c &&
+	test_tick &&
+	git commit -m initial &&
+
+	grep -v Classic <hello.c >hello.c.new &&
+	mv hello.c.new hello.c
+'
+
+cat <<\EOF >expected
+diff --git a/hello.c b/hello.c
+--- a/hello.c
++++ b/hello.c
+@@ -10,8 +10,7 @@ static int a(void)
+ static int hello_world(void)
+ {
+-	/* Classic. */
+ 	printf("Hello world.\n");
+ 
+ 	/* Success! */
+ 	return 0;
+ }
+EOF
+
+test_expect_success 'diff -U0 -W' '
+	git diff -U0 -W >actual &&
+	compare_diff_patch actual expected
+'
+
+cat <<\EOF >expected
+diff --git a/hello.c b/hello.c
+--- a/hello.c
++++ b/hello.c
+@@ -9,9 +9,8 @@ static int a(void)
+ 
+ static int hello_world(void)
+ {
+-	/* Classic. */
+ 	printf("Hello world.\n");
+ 
+ 	/* Success! */
+ 	return 0;
+ }
+EOF
+
+test_expect_success 'diff -W' '
+	git diff -W >actual &&
+	compare_diff_patch actual expected
+'
+
+test_done

xdiff/xdiff.h

@@ -43,6 +43,7 @@ extern "C" {
 
 #define XDL_EMIT_FUNCNAMES (1 << 0)
 #define XDL_EMIT_COMMON (1 << 1)
+#define XDL_EMIT_FUNCCONTEXT (1 << 2)
 
 #define XDL_MMB_READONLY (1 << 0)
 

xdiff/xemit.c

@@ -100,14 +100,40 @@ static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 	return 0;
 }
 
+struct func_line {
+	long len;
+	char buf[80];
+};
+
+static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
+			  struct func_line *func_line, long start, long limit)
+{
+	find_func_t ff = xecfg->find_func ? xecfg->find_func : def_ff;
+	long l, size, step = (start > limit) ? -1 : 1;
+	char *buf, dummy[1];
+
+	buf = func_line ? func_line->buf : dummy;
+	size = func_line ? sizeof(func_line->buf) : sizeof(dummy);
+
+	for (l = start; l != limit && 0 <= l && l < xe->xdf1.nrec; l += step) {
+		const char *rec;
+		long reclen = xdl_get_rec(&xe->xdf1, l, &rec);
+		long len = ff(rec, reclen, buf, size, xecfg->find_func_priv);
+		if (len >= 0) {
+			if (func_line)
+				func_line->len = len;
+			return l;
+		}
+	}
+	return -1;
+}
+
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg) {
 	long s1, s2, e1, e2, lctx;
 	xdchange_t *xch, *xche;
-	char funcbuf[80];
-	long funclen = 0;
 	long funclineprev = -1;
-	find_func_t ff = xecfg->find_func ?  xecfg->find_func : def_ff;
+	struct func_line func_line = { 0 };
 
 	if (xecfg->flags & XDL_EMIT_COMMON)
 		return xdl_emit_common(xe, xscr, ecb, xecfg);
@@ -118,6 +144,17 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		s1 = XDL_MAX(xch->i1 - xecfg->ctxlen, 0);
 		s2 = XDL_MAX(xch->i2 - xecfg->ctxlen, 0);
 
+		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {
+			long fs1 = get_func_line(xe, xecfg, NULL, xch->i1, -1);
+			if (fs1 < 0)
+				fs1 = 0;
+			if (fs1 < s1) {
+				s2 -= s1 - fs1;
+				s1 = fs1;
+			}
+		}
+
+ again:
 		lctx = xecfg->ctxlen;
 		lctx = XDL_MIN(lctx, xe->xdf1.nrec - (xche->i1 + xche->chg1));
 		lctx = XDL_MIN(lctx, xe->xdf2.nrec - (xche->i2 + xche->chg2));
@@ -125,27 +162,43 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		e1 = xche->i1 + xche->chg1 + lctx;
 		e2 = xche->i2 + xche->chg2 + lctx;
 
+		if (xecfg->flags & XDL_EMIT_FUNCCONTEXT) {
+			long fe1 = get_func_line(xe, xecfg, NULL,
+						 xche->i1 + xche->chg1,
+						 xe->xdf1.nrec);
+			if (fe1 < 0)
+				fe1 = xe->xdf1.nrec;
+			if (fe1 > e1) {
+				e2 += fe1 - e1;
+				e1 = fe1;
+			}
+
+			/*
+			 * Overlap with next change?  Then include it
+			 * in the current hunk and start over to find
+			 * its new end.
+			 */
+			if (xche->next) {
+				long l = xche->next->i1;
+				if (l <= e1 ||
+				    get_func_line(xe, xecfg, NULL, l, e1) < 0) {
+					xche = xche->next;
+					goto again;
+				}
+			}
+		}
+
 		/*
 		 * Emit current hunk header.
 		 */
 
 		if (xecfg->flags & XDL_EMIT_FUNCNAMES) {
-			long l;
+			get_func_line(xe, xecfg, &func_line,
-			for (l = s1 - 1; l >= 0 && l > funclineprev; l--) {
+				      s1 - 1, funclineprev);
-				const char *rec;
-				long reclen = xdl_get_rec(&xe->xdf1, l, &rec);
-				long newfunclen = ff(rec, reclen, funcbuf,
-						     sizeof(funcbuf),
-						     xecfg->find_func_priv);
-				if (newfunclen >= 0) {
-					funclen = newfunclen;
-					break;
-				}
-			}
 			funclineprev = s1 - 1;
 		}
 		if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
-				      funcbuf, funclen, ecb) < 0)
+				      func_line.buf, func_line.len, ecb) < 0)
 			return -1;
 
 		/*