Merge branch 'cb/diff-fname-optim' into maint

* cb/diff-fname-optim:
  diff: avoid repeated scanning while looking for funcname
  do not search functions for patch ID
  add rebase patch id tests

diff.c

@@ -3870,7 +3870,7 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 
 		xpp.flags = 0;
 		xecfg.ctxlen = 3;
-		xecfg.flags = XDL_EMIT_FUNCNAMES;
+		xecfg.flags = 0;
 		xdi_diff_outf(&mf1, &mf2, patch_id_consume, &data,
 			      &xpp, &xecfg);
 	}

t/t3419-rebase-patch-id.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+
+test_description='git rebase - test patch id computation'
+
+. ./test-lib.sh
+
+test_set_prereq NOT_EXPENSIVE
+test -n "$GIT_PATCHID_TIMING_TESTS" && test_set_prereq EXPENSIVE
+test -x /usr/bin/time && test_set_prereq USR_BIN_TIME
+
+count()
+{
+	i=0
+	while test $i -lt $1
+	do
+		echo "$i"
+		i=$(($i+1))
+	done
+}
+
+scramble()
+{
+	i=0
+	while read x
+	do
+		if test $i -ne 0
+		then
+			echo "$x"
+		fi
+		i=$(((i+1) % 10))
+	done < "$1" > "$1.new"
+	mv -f "$1.new" "$1"
+}
+
+run()
+{
+	echo \$ "$@"
+	/usr/bin/time "$@" >/dev/null
+}
+
+test_expect_success 'setup' '
+	git commit --allow-empty -m initial
+	git tag root
+'
+
+do_tests()
+{
+	pr=$1
+	nlines=$2
+
+	test_expect_success $pr "setup: $nlines lines" "
+		rm -f .gitattributes &&
+		git checkout -q -f master &&
+		git reset --hard root &&
+		count $nlines >file &&
+		git add file &&
+		git commit -q -m initial &&
+		git branch -f other &&
+
+		scramble file &&
+		git add file &&
+		git commit -q -m 'change big file' &&
+
+		git checkout -q other &&
+		: >newfile &&
+		git add newfile &&
+		git commit -q -m 'add small file' &&
+
+		git cherry-pick master >/dev/null 2>&1
+	"
+
+	test_debug "
+		run git diff master^\!
+	"
+
+	test_expect_success $pr 'setup attributes' "
+		echo 'file binary' >.gitattributes
+	"
+
+	test_debug "
+		run git format-patch --stdout master &&
+		run git format-patch --stdout --ignore-if-in-upstream master
+	"
+
+	test_expect_success $pr 'detect upstream patch' "
+		git checkout -q master &&
+		scramble file &&
+		git add file &&
+		git commit -q -m 'change big file again' &&
+		git checkout -q other^{} &&
+		git rebase master &&
+		test_must_fail test -n \"\$(git rev-list master...HEAD~)\"
+	"
+
+	test_expect_success $pr 'do not drop patch' "
+		git branch -f squashed master &&
+		git checkout -q -f squashed &&
+		git reset -q --soft HEAD~2 &&
+		git commit -q -m squashed &&
+		git checkout -q other^{} &&
+		test_must_fail git rebase squashed &&
+		rm -rf .git/rebase-apply
+	"
+}
+
+do_tests NOT_EXPENSIVE 500
+do_tests EXPENSIVE 50000
+
+test_done

xdiff/xemit.c

@@ -85,27 +85,6 @@ static long def_ff(const char *rec, long len, char *buf, long sz, void *priv)
 	return -1;
 }
 
-static void xdl_find_func(xdfile_t *xf, long i, char *buf, long sz, long *ll,
-		find_func_t ff, void *ff_priv) {
-
-	/*
-	 * Be quite stupid about this for now.  Find a line in the old file
-	 * before the start of the hunk (and context) which starts with a
-	 * plausible character.
-	 */
-
-	const char *rec;
-	long len;
-
-	while (i-- > 0) {
-		len = xdl_get_rec(xf, i, &rec);
-		if ((*ll = ff(rec, len, buf, sz, ff_priv)) >= 0)
-			return;
-	}
-	*ll = 0;
-}
-
-
 static int xdl_emit_common(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
                            xdemitconf_t const *xecfg) {
 	xdfile_t *xdf = &xe->xdf1;
@@ -127,6 +106,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 	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;
 
 	if (xecfg->flags & XDL_EMIT_COMMON)
@@ -150,9 +130,19 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 		 */
 
 		if (xecfg->flags & XDL_EMIT_FUNCNAMES) {
-			xdl_find_func(&xe->xdf1, s1, funcbuf,
-				      sizeof(funcbuf), &funclen,
-				      ff, xecfg->find_func_priv);
+			long l;
+			for (l = s1 - 1; l >= 0 && l > funclineprev; l--) {
+				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)