diff --git a/grep.c b/grep.c
index ec6f7ffa196..1e15b6292d7 100644
--- a/grep.c
+++ b/grep.c
@@ -1396,9 +1396,17 @@ static int fill_textconv_grep(struct userdiff_driver *driver,
 	return 0;
 }
 
+static int is_empty_line(const char *bol, const char *eol)
+{
+	while (bol < eol && isspace(*bol))
+		bol++;
+	return bol == eol;
+}
+
 static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int collect_hits)
 {
 	char *bol;
+	char *peek_bol = NULL;
 	unsigned long left;
 	unsigned lno = 1;
 	unsigned last_hit = 0;
@@ -1543,8 +1551,24 @@ static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int colle
 				show_function = 1;
 			goto next_line;
 		}
-		if (show_function && match_funcname(opt, gs, bol, eol))
-			show_function = 0;
+		if (show_function && (!peek_bol || peek_bol < bol)) {
+			unsigned long peek_left = left;
+			char *peek_eol = eol;
+
+			/*
+			 * Trailing empty lines are not interesting.
+			 * Peek past them to see if they belong to the
+			 * body of the current function.
+			 */
+			peek_bol = bol;
+			while (is_empty_line(peek_bol, peek_eol)) {
+				peek_bol = peek_eol + 1;
+				peek_eol = end_of_line(peek_bol, &peek_left);
+			}
+
+			if (match_funcname(opt, gs, peek_bol, peek_eol))
+				show_function = 0;
+		}
 		if (show_function ||
 		    (last_hit && lno <= last_hit + opt->post_context)) {
 			/* If the last hit is within the post context,
diff --git a/t/t4051-diff-function-context.sh b/t/t4051-diff-function-context.sh
index 001d678e09b..b79b87790b2 100755
--- a/t/t4051-diff-function-context.sh
+++ b/t/t4051-diff-function-context.sh
@@ -3,90 +3,180 @@
 test_description='diff function context'
 
 . ./test-lib.sh
-. "$TEST_DIRECTORY"/diff-lib.sh
 
+dir="$TEST_DIRECTORY/t4051"
 
-cat <<\EOF >hello.c
-#include <stdio.h>
-
-static int a(void)
-{
-	/*
-	 * Dummy.
-	 */
+commit_and_tag () {
+	tag=$1 &&
+	shift &&
+	git add "$@" &&
+	test_tick &&
+	git commit -m "$tag" &&
+	git tag "$tag"
 }
 
-static int hello_world(void)
-{
-	/* Classic. */
-	printf("Hello world.\n");
-
-	/* Success! */
-	return 0;
-}
-static int b(void)
-{
-	/*
-	 * Dummy, too.
-	 */
+first_context_line () {
+	awk '
+		found {print; exit}
+		/^@@/ {found = 1}
+	'
 }
 
-int main(int argc, char **argv)
-{
-	a();
-	b();
-	return hello_world();
+last_context_line () {
+	sed -ne \$p
+}
+
+check_diff () {
+	name=$1
+	desc=$2
+	options="-W $3"
+
+	test_expect_success "$desc" '
+		git diff $options "$name^" "$name" >"$name.diff"
+	'
+
+	test_expect_success ' diff applies' '
+		test_when_finished "git reset --hard" &&
+		git checkout --detach "$name^" &&
+		git apply --index "$name.diff" &&
+		git diff --exit-code "$name"
+	'
 }
-EOF
 
 test_expect_success 'setup' '
-	git add hello.c &&
-	test_tick &&
-	git commit -m initial &&
+	cat "$dir/includes.c" "$dir/dummy.c" "$dir/dummy.c" "$dir/hello.c" \
+		"$dir/dummy.c" "$dir/dummy.c" >file.c &&
+	commit_and_tag initial file.c &&
 
-	grep -v Classic <hello.c >hello.c.new &&
-	mv hello.c.new hello.c
+	grep -v "delete me from hello" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag changed_hello file.c &&
+
+	grep -v "delete me from includes" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag changed_includes file.c &&
+
+	cat "$dir/appended1.c" >>file.c &&
+	commit_and_tag appended file.c &&
+
+	cat "$dir/appended2.c" >>file.c &&
+	commit_and_tag extended file.c &&
+
+	grep -v "Begin of second part" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag long_common_tail file.c &&
+
+	git checkout initial &&
+	grep -v "delete me from hello" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	cat "$dir/appended1.c" >>file.c &&
+	commit_and_tag changed_hello_appended file.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
+check_diff changed_hello 'changed function'
 
-test_expect_success 'diff -U0 -W' '
-	git diff -U0 -W >actual &&
-	compare_diff_patch actual expected
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of hello" changed_hello.diff
 '
 
-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 ' context includes end' '
+	grep "^ .*End of hello" changed_hello.diff
+'
 
-test_expect_success 'diff -W' '
-	git diff -W >actual &&
-	compare_diff_patch actual expected
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_hello.diff) -le 1
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <changed_hello.diff)" != " "
+'
+
+test_expect_success ' context does not include trailing empty lines' '
+	test "$(last_context_line <changed_hello.diff)" != " "
+'
+
+check_diff changed_includes 'changed includes'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin.h" changed_includes.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End.h" changed_includes.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_includes.diff) -le 1
+'
+
+test_expect_success ' context does not include trailing empty lines' '
+	test "$(last_context_line <changed_includes.diff)" != " "
+'
+
+check_diff appended 'appended function'
+
+test_expect_success ' context includes begin' '
+	grep "^[+].*Begin of first part" appended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^[+].*End of first part" appended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" appended.diff) -le 1
+'
+
+check_diff extended 'appended function part'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of first part" extended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^[+].*End of second part" extended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" extended.diff) -le 2
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <extended.diff)" != " "
+'
+
+check_diff long_common_tail 'change with long common tail and no context' -U0
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of first part" long_common_tail.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End of second part" long_common_tail.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" long_common_tail.diff) -le 2
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <long_common_tail.diff.diff)" != " "
+'
+
+check_diff changed_hello_appended 'changed function plus appended function'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of hello" changed_hello_appended.diff &&
+	grep "^[+].*Begin of first part" changed_hello_appended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End of hello" changed_hello_appended.diff &&
+	grep "^[+].*End of first part" changed_hello_appended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_hello_appended.diff) -le 2
 '
 
 test_done
diff --git a/t/t4051/appended1.c b/t/t4051/appended1.c
new file mode 100644
index 00000000000..a9f56f11db3
--- /dev/null
+++ b/t/t4051/appended1.c
@@ -0,0 +1,15 @@
+
+int appended(void) // Begin of first part
+{
+	int i;
+	char *s = "a string";
+
+	printf("%s\n", s);
+
+	for (i = 99;
+	     i >= 0;
+	     i--) {
+		printf("%d bottles of beer on the wall\n", i);
+	}
+
+	printf("End of first part\n");
diff --git a/t/t4051/appended2.c b/t/t4051/appended2.c
new file mode 100644
index 00000000000..e651f7147b9
--- /dev/null
+++ b/t/t4051/appended2.c
@@ -0,0 +1,35 @@
+	printf("Begin of second part\n");
+
+	/*
+	 * Lorem ipsum dolor sit amet, consectetuer sadipscing elitr,
+	 * sed diam nonumy eirmod tempor invidunt ut labore et dolore
+	 * magna aliquyam erat, sed diam voluptua. At vero eos et
+	 * accusam et justo duo dolores et ea rebum. Stet clita kasd
+	 * gubergren, no sea takimata sanctus est Lorem ipsum dolor
+	 * sit amet.
+	 *
+	 * Lorem ipsum dolor sit amet, consectetuer sadipscing elitr,
+	 * sed diam nonumy eirmod tempor invidunt ut labore et dolore
+	 * magna aliquyam erat, sed diam voluptua. At vero eos et
+	 * accusam et justo duo dolores et ea rebum. Stet clita kasd
+	 * gubergren, no sea takimata sanctus est Lorem ipsum dolor
+	 * sit amet.
+	 *
+	 * Lorem ipsum dolor sit amet, consectetuer sadipscing elitr,
+	 * sed diam nonumy eirmod tempor invidunt ut labore et dolore
+	 * magna aliquyam erat, sed diam voluptua. At vero eos et
+	 * accusam et justo duo dolores et ea rebum. Stet clita kasd
+	 * gubergren, no sea takimata sanctus est Lorem ipsum dolor
+	 * sit amet.
+	 *
+	 * Lorem ipsum dolor sit amet, consectetuer sadipscing elitr,
+	 * sed diam nonumy eirmod tempor invidunt ut labore et dolore
+	 * magna aliquyam erat, sed diam voluptua. At vero eos et
+	 * accusam et justo duo dolores et ea rebum. Stet clita kasd
+	 * gubergren, no sea takimata sanctus est Lorem ipsum dolor
+	 * sit amet.
+	 *
+	 */
+
+	return 0;
+}	// End of second part
diff --git a/t/t4051/dummy.c b/t/t4051/dummy.c
new file mode 100644
index 00000000000..a43016e870f
--- /dev/null
+++ b/t/t4051/dummy.c
@@ -0,0 +1,7 @@
+
+static int dummy(void)	// Begin of dummy
+{
+	int rc = 0;
+
+	return rc;
+}	// End of dummy
diff --git a/t/t4051/hello.c b/t/t4051/hello.c
new file mode 100644
index 00000000000..63b1a1e4efb
--- /dev/null
+++ b/t/t4051/hello.c
@@ -0,0 +1,21 @@
+
+static void hello(void)	// Begin of hello
+{
+	/*
+	 * Classic.
+	 */
+	putchar('H');
+	putchar('e');
+	putchar('l');
+	putchar('l');
+	putchar('o');
+	putchar(' ');
+	/* delete me from hello */
+	putchar('w');
+	putchar('o');
+	putchar('r');
+	putchar('l');
+	putchar('d');
+	putchar('.');
+	putchar('\n');
+}	// End of hello
diff --git a/t/t4051/includes.c b/t/t4051/includes.c
new file mode 100644
index 00000000000..efc68f8bf6d
--- /dev/null
+++ b/t/t4051/includes.c
@@ -0,0 +1,20 @@
+#include <Begin.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdarg.h>
+/* delete me from includes */
+#include <string.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <sys/time.h>
+#include <time.h>
+#include <signal.h>
+#include <assert.h>
+#include <regex.h>
+#include <utime.h>
+#include <syslog.h>
+#include <End.h>
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 1e72971a165..960425a4ec6 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -9,7 +9,9 @@ test_description='git grep various.
 . ./test-lib.sh
 
 cat >hello.c <<EOF
+#include <assert.h>
 #include <stdio.h>
+
 int main(int argc, const char **argv)
 {
 	printf("Hello world.\n");
@@ -715,6 +717,7 @@ test_expect_success 'grep -p' '
 
 cat >expected <<EOF
 hello.c-#include <stdio.h>
+hello.c-
 hello.c=int main(int argc, const char **argv)
 hello.c-{
 hello.c-	printf("Hello world.\n");
@@ -740,6 +743,16 @@ test_expect_success 'grep -W' '
 	test_cmp expected actual
 '
 
+cat >expected <<EOF
+hello.c-#include <assert.h>
+hello.c:#include <stdio.h>
+EOF
+
+test_expect_success 'grep -W shows no trailing empty lines' '
+	git grep -W stdio >actual &&
+	test_cmp expected actual
+'
+
 cat >expected <<EOF
 hello.c=	printf("Hello world.\n");
 hello.c:	return 0;
@@ -1232,8 +1245,8 @@ test_expect_success 'grep --heading' '
 
 cat >expected <<EOF
 <BOLD;GREEN>hello.c<RESET>
-2:int main(int argc, const <BLACK;BYELLOW>char<RESET> **argv)
-6:	/* <BLACK;BYELLOW>char<RESET> ?? */
+4:int main(int argc, const <BLACK;BYELLOW>char<RESET> **argv)
+8:	/* <BLACK;BYELLOW>char<RESET> ?? */
 
 <BOLD;GREEN>hello_world<RESET>
 3:Hel<BLACK;BYELLOW>lo_w<RESET>orld
@@ -1340,7 +1353,7 @@ test_expect_success 'grep --color -e A --and --not -e B with context' '
 '
 
 cat >expected <<EOF
-hello.c-#include <stdio.h>
+hello.c-
 hello.c=int main(int argc, const char **argv)
 hello.c-{
 hello.c:	pr<RED>int<RESET>f("<RED>Hello<RESET> world.\n");
diff --git a/xdiff-interface.c b/xdiff-interface.c
index 54236f24b97..f34ea762e47 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -100,9 +100,9 @@ static int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
 
 /*
  * Trim down common substring at the end of the buffers,
- * but leave at least ctx lines at the end.
+ * but end on a complete line.
  */
-static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
+static void trim_common_tail(mmfile_t *a, mmfile_t *b)
 {
 	const int blk = 1024;
 	long trimmed = 0, recovered = 0;
@@ -110,9 +110,6 @@ static void trim_common_tail(mmfile_t *a, mmfile_t *b, long ctx)
 	char *bp = b->ptr + b->size;
 	long smaller = (a->size < b->size) ? a->size : b->size;
 
-	if (ctx)
-		return;
-
 	while (blk + trimmed <= smaller && !memcmp(ap - blk, bp - blk, blk)) {
 		trimmed += blk;
 		ap -= blk;
@@ -134,7 +131,8 @@ int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t co
 	if (mf1->size > MAX_XDIFF_SIZE || mf2->size > MAX_XDIFF_SIZE)
 		return -1;
 
-	trim_common_tail(&a, &b, xecfg->ctxlen);
+	if (!xecfg->ctxlen && !(xecfg->flags & XDL_EMIT_FUNCCONTEXT))
+		trim_common_tail(&a, &b);
 
 	return xdl_diff(&a, &b, xpp, xecfg, xecb);
 }
diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 993724b11c4..49aa16ff78d 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -120,6 +120,16 @@ static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)
 	return -1;
 }
 
+static long match_func_rec(xdfile_t *xdf, xdemitconf_t const *xecfg, long ri,
+			   char *buf, long sz)
+{
+	const char *rec;
+	long len = xdl_get_rec(xdf, ri, &rec);
+	if (!xecfg->find_func)
+		return def_ff(rec, len, buf, sz, xecfg->find_func_priv);
+	return xecfg->find_func(rec, len, buf, sz, xecfg->find_func_priv);
+}
+
 struct func_line {
 	long len;
 	char buf[80];
@@ -128,7 +138,6 @@ struct func_line {
 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];
 
@@ -136,9 +145,7 @@ static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
 	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);
+		long len = match_func_rec(&xe->xdf1, xecfg, l, buf, size);
 		if (len >= 0) {
 			if (func_line)
 				func_line->len = len;
@@ -148,6 +155,18 @@ static long get_func_line(xdfenv_t *xe, xdemitconf_t const *xecfg,
 	return -1;
 }
 
+static int is_empty_rec(xdfile_t *xdf, long ri)
+{
+	const char *rec;
+	long len = xdl_get_rec(xdf, ri, &rec);
+
+	while (len > 0 && XDL_ISSPACE(*rec)) {
+		rec++;
+		len--;
+	}
+	return !len;
+}
+
 int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		  xdemitconf_t const *xecfg) {
 	long s1, s2, e1, e2, lctx;
@@ -164,7 +183,34 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		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);
+			long fs1, i1 = xch->i1;
+
+			/* Appended chunk? */
+			if (i1 >= xe->xdf1.nrec) {
+				char dummy[1];
+				long i2 = xch->i2;
+
+				/*
+				 * We don't need additional context if
+				 * a whole function was added, possibly
+				 * starting with empty lines.
+				 */
+				while (i2 < xe->xdf2.nrec &&
+				       is_empty_rec(&xe->xdf2, i2))
+					i2++;
+				if (i2 < xe->xdf2.nrec &&
+				    match_func_rec(&xe->xdf2, xecfg, i2,
+						   dummy, sizeof(dummy)) >= 0)
+					goto post_context_calculation;
+
+				/*
+				 * Otherwise get more context from the
+				 * pre-image.
+				 */
+				i1 = xe->xdf1.nrec - 1;
+			}
+
+			fs1 = get_func_line(xe, xecfg, NULL, i1, -1);
 			if (fs1 < 0)
 				fs1 = 0;
 			if (fs1 < s1) {
@@ -173,7 +219,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 			}
 		}
 
- again:
+ post_context_calculation:
 		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));
@@ -185,6 +231,8 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 			long fe1 = get_func_line(xe, xecfg, NULL,
 						 xche->i1 + xche->chg1,
 						 xe->xdf1.nrec);
+			while (fe1 > 0 && is_empty_rec(&xe->xdf1, fe1 - 1))
+				fe1--;
 			if (fe1 < 0)
 				fe1 = xe->xdf1.nrec;
 			if (fe1 > e1) {
@@ -198,11 +246,12 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 			 * its new end.
 			 */
 			if (xche->next) {
-				long l = xche->next->i1;
+				long l = XDL_MIN(xche->next->i1,
+						 xe->xdf1.nrec - 1);
 				if (l <= e1 ||
 				    get_func_line(xe, xecfg, NULL, l, e1) < 0) {
 					xche = xche->next;
-					goto again;
+					goto post_context_calculation;
 				}
 			}
 		}