19 files changed, 303 insertions, 128 deletions

diff --git a/t/check-non-portable-shell.pl b/t/check-non-portable-shell.pl
index 166d64d4a2..38bfeebd88 100755
--- a/t/check-non-portable-shell.pl
+++ b/t/check-non-portable-shell.pl
@@ -27,14 +27,14 @@ for my $i (@ARGV) {
 	close $f;
 }
 
+my $line = '';
 while (<>) {
 	chomp;
+	$line .= $_;
 	# stitch together incomplete lines (those ending with "\")
-	while (s/\\$//) {
-		$_ .= readline;
-		chomp;
-	}
+	next if $line =~ s/\\$//;
 
+	$_ = $line;
 	/\bcp\s+-a/ and err 'cp -a is not portable';
 	/\bsed\s+-[^efn]\s+/ and err 'sed option not portable (use only -n, -e, -f)';
 	/\becho\s+-[neE]/ and err 'echo with option is not portable (use printf)';
@@ -48,6 +48,7 @@ while (<>) {
 	/\bexport\s+[A-Za-z0-9_]*=/ and err '"export FOO=bar" is not portable (use FOO=bar && export FOO)';
 	/^\s*([A-Z0-9_]+=(\w+|(["']).*?\3)\s+)+(\w+)/ and exists($func{$4}) and
 		err '"FOO=bar shell_func" assignment extends beyond "shell_func"';
+	$line = '';
 	# this resets our $. for each file
 	close ARGV if eof;
 }
diff --git a/t/helper/test-parse-options.c b/t/helper/test-parse-options.c
index 2232b2f79e..af82db06ac 100644
--- a/t/helper/test-parse-options.c
+++ b/t/helper/test-parse-options.c
@@ -149,6 +149,9 @@ int cmd__parse_options(int argc, const char **argv)
 		OPT_CALLBACK(0, "expect", &expect, "string",
 			     "expected output in the variable dump",
 			     collect_expect),
+		OPT_GROUP("Alias"),
+		OPT_STRING('A', "alias-source", &string, "string", "get a string"),
+		OPT_ALIAS('Z', "alias-target", "alias-source"),
 		OPT_END(),
 	};
 	int i;
diff --git a/t/helper/test-read-cache.c b/t/helper/test-read-cache.c
index d674c88ba0..7e79b555de 100644
--- a/t/helper/test-read-cache.c
+++ b/t/helper/test-read-cache.c
@@ -1,14 +1,36 @@
 #include "test-tool.h"
 #include "cache.h"
+#include "config.h"
 
 int cmd__read_cache(int argc, const char **argv)
 {
-	int i, cnt = 1;
+	int i, cnt = 1, namelen;
+	const char *name = NULL;
+
+	if (argc > 1 && skip_prefix(argv[1], "--print-and-refresh=", &name)) {
+		namelen = strlen(name);
+		argc--;
+		argv++;
+	}
+
 	if (argc == 2)
 		cnt = strtol(argv[1], NULL, 0);
 	setup_git_directory();
+	git_config(git_default_config, NULL);
 	for (i = 0; i < cnt; i++) {
 		read_cache();
+		if (name) {
+			int pos;
+
+			refresh_index(&the_index, REFRESH_QUIET,
+				      NULL, NULL, NULL);
+			pos = index_name_pos(&the_index, name, namelen);
+			if (pos < 0)
+				die("%s not in index", name);
+			printf("%s is%s up to date\n", name,
+			       ce_uptodate(the_index.cache[pos]) ? "" : " not");
+			write_file(name, "%d\n", i);
+		}
 		discard_cache();
 	}
 	return 0;
diff --git a/t/lib-httpd/apache.conf b/t/lib-httpd/apache.conf
index 06a81b54c7..5c1c86c193 100644
--- a/t/lib-httpd/apache.conf
+++ b/t/lib-httpd/apache.conf
@@ -76,6 +76,7 @@ PassEnv GIT_VALGRIND
 PassEnv GIT_VALGRIND_OPTIONS
 PassEnv GNUPGHOME
 PassEnv ASAN_OPTIONS
+PassEnv LSAN_OPTIONS
 PassEnv GIT_TRACE
 PassEnv GIT_CONFIG_NOSYSTEM
 PassEnv GIT_TEST_SIDEBAND_ALL
diff --git a/t/perf/README b/t/perf/README
index be12090c38..c7b70e2d28 100644
--- a/t/perf/README
+++ b/t/perf/README
@@ -45,7 +45,7 @@ call the aggregation script to summarize the results:
 
     $ ./p0001-rev-list.sh
     [...]
-    $ GIT_BUILD_DIR=/path/to/other/git ./p0001-rev-list.sh
+    $ ./run /path/to/other/git -- ./p0001-rev-list.sh
     [...]
     $ ./aggregate.perl . /path/to/other/git ./p0001-rev-list.sh
 
diff --git a/t/perf/aggregate.perl b/t/perf/aggregate.perl
index 76dd48f890..66554d2161 100755
--- a/t/perf/aggregate.perl
+++ b/t/perf/aggregate.perl
@@ -5,6 +5,7 @@ use strict;
 use warnings;
 use Getopt::Long;
 use Git;
+use Cwd qw(realpath);
 
 sub get_times {
 	my $name = shift;
@@ -98,18 +99,21 @@ usage() unless $rc;
 while (scalar @ARGV) {
 	my $arg = $ARGV[0];
 	my $dir;
+	my $prefix = '';
 	last if -f $arg or $arg eq "--";
 	if (! -d $arg) {
 		my $rev = Git::command_oneline(qw(rev-parse --verify), $arg);
 		$dir = "build/".$rev;
+	} elsif ($arg eq '.') {
+		$dir = '.';
 	} else {
-		$arg =~ s{/*$}{};
-		$dir = $arg;
-		$dirabbrevs{$dir} = $dir;
+		$dir = realpath($arg);
+		$dirnames{$dir} = $dir;
+		$prefix .= 'bindir';
 	}
 	push @dirs, $dir;
-	$dirnames{$dir} = $arg;
-	my $prefix = $dir;
+	$dirnames{$dir} ||= $arg;
+	$prefix .= $dir;
 	$prefix =~ tr/^a-zA-Z0-9/_/c;
 	$prefixes{$dir} = $prefix . '.';
 	shift @ARGV;
@@ -311,9 +315,6 @@ sub print_codespeed_results {
 		$environment = $reponame;
 	} elsif (exists $ENV{GIT_PERF_REPO_NAME} and $ENV{GIT_PERF_REPO_NAME} ne "") {
 		$environment = $ENV{GIT_PERF_REPO_NAME};
-	} elsif (exists $ENV{GIT_TEST_INSTALLED} and $ENV{GIT_TEST_INSTALLED} ne "") {
-		$environment = $ENV{GIT_TEST_INSTALLED};
-		$environment =~ s|/bin-wrappers$||;
 	} else {
 		$environment = `uname -r`;
 		chomp $environment;
diff --git a/t/perf/perf-lib.sh b/t/perf/perf-lib.sh
index 169f92eae3..b58a43ea43 100644
--- a/t/perf/perf-lib.sh
+++ b/t/perf/perf-lib.sh
@@ -21,19 +21,21 @@
 # because it will change our working directory.
 TEST_DIRECTORY=$(pwd)/..
 TEST_OUTPUT_DIRECTORY=$(pwd)
-ABSOLUTE_GIT_TEST_INSTALLED=$(
-	test -n "$GIT_TEST_INSTALLED" && cd "$GIT_TEST_INSTALLED" && pwd)
 
 TEST_NO_CREATE_REPO=t
 TEST_NO_MALLOC_CHECK=t
 
 . ../test-lib.sh
 
-if test -z "$GIT_TEST_INSTALLED"; then
-	perf_results_prefix=
-else
-	perf_results_prefix=$(printf "%s" "${GIT_TEST_INSTALLED%/bin-wrappers}" | tr -c "[a-zA-Z0-9]" "[_*]")"."
-	GIT_TEST_INSTALLED=$ABSOLUTE_GIT_TEST_INSTALLED
+if test -n "$GIT_TEST_INSTALLED" -a -z "$PERF_SET_GIT_TEST_INSTALLED"
+then
+	error "Do not use GIT_TEST_INSTALLED with the perf tests.
+
+Instead use:
+
+    ./run <path-to-git> -- <tests>
+
+See t/perf/README for details."
 fi
 
 # Variables from test-lib that are normally internal to the tests; we
@@ -179,7 +181,7 @@ test_wrapper_ () {
 		base=$(basename "$0" .sh)
 		echo "$test_count" >>"$perf_results_dir"/$base.subtests
 		echo "$1" >"$perf_results_dir"/$base.$test_count.descr
-		base="$perf_results_dir"/"$perf_results_prefix$(basename "$0" .sh)"."$test_count"
+		base="$perf_results_dir"/"$PERF_RESULTS_PREFIX$(basename "$0" .sh)"."$test_count"
 		"$test_wrapper_func_" "$@"
 	fi
 
diff --git a/t/perf/run b/t/perf/run
index 9aaa733c77..c7b86104e1 100755
--- a/t/perf/run
+++ b/t/perf/run
@@ -70,6 +70,24 @@ build_git_rev () {
 	) || die "failed to build revision '$mydir'"
 }
 
+set_git_test_installed () {
+	mydir=$1
+
+	mydir_abs=$(cd $mydir && pwd)
+	mydir_abs_wrappers="$mydir_abs_wrappers/bin-wrappers"
+	if test -d "$mydir_abs_wrappers"
+	then
+		GIT_TEST_INSTALLED=$mydir_abs_wrappers
+	else
+		# Older versions of git lacked bin-wrappers;
+		# fallback to the files in the root.
+		GIT_TEST_INSTALLED=$mydir_abs
+	fi
+	export GIT_TEST_INSTALLED
+	PERF_SET_GIT_TEST_INSTALLED=true
+	export PERF_SET_GIT_TEST_INSTALLED
+}
+
 run_dirs_helper () {
 	mydir=${1%/}
 	shift
@@ -79,7 +97,16 @@ run_dirs_helper () {
 	if test $# -gt 0 -a "$1" = --; then
 		shift
 	fi
-	if [ ! -d "$mydir" ]; then
+
+	PERF_RESULTS_PREFIX=
+	if test "$mydir" = "."
+	then
+		unset GIT_TEST_INSTALLED
+	elif test -d "$mydir"
+	then
+		PERF_RESULTS_PREFIX=bindir$(cd $mydir && printf "%s" "$(pwd)" | tr -c "[a-zA-Z0-9]" "_").
+		set_git_test_installed "$mydir"
+	else
 		rev=$(git rev-parse --verify "$mydir" 2>/dev/null) ||
 		die "'$mydir' is neither a directory nor a valid revision"
 		if [ ! -d build/$rev ]; then
@@ -87,16 +114,12 @@ run_dirs_helper () {
 		fi
 		build_git_rev $rev "$mydir"
 		mydir=build/$rev
+
+		PERF_RESULTS_PREFIX=build_$rev.
+		set_git_test_installed "$mydir"
 	fi
-	if test "$mydir" = .; then
-		unset GIT_TEST_INSTALLED
-	else
-		GIT_TEST_INSTALLED="$mydir/bin-wrappers"
-		# Older versions of git lacked bin-wrappers; fallback to the
-		# files in the root.
-		test -d "$GIT_TEST_INSTALLED" || GIT_TEST_INSTALLED=$mydir
-		export GIT_TEST_INSTALLED
-	fi
+	export PERF_RESULTS_PREFIX
+
 	run_one_dir "$@"
 }
 
diff --git a/t/t0040-parse-options.sh b/t/t0040-parse-options.sh
index 800b3ea5f5..cebc77fab0 100755
--- a/t/t0040-parse-options.sh
+++ b/t/t0040-parse-options.sh
@@ -48,6 +48,12 @@ Standard options
     -q, --quiet           be quiet
     --expect <string>     expected output in the variable dump
 
+Alias
+    -A, --alias-source <string>
+                          get a string
+    -Z, --alias-target <string>
+                          get a string
+
 EOF
 
 test_expect_success 'test help' '
@@ -224,6 +230,17 @@ test_expect_success 'non ambiguous option (after two options it abbreviates)' '
 	test-tool parse-options --expect="string: 123" --st 123
 '
 
+test_expect_success 'Alias options do not contribute to abbreviation' '
+	test-tool parse-options --alias-source 123 >output &&
+	grep "^string: 123" output &&
+	test-tool parse-options --alias-target 123 >output &&
+	grep "^string: 123" output &&
+	test_must_fail test-tool parse-options --alias &&
+	GIT_TEST_DISALLOW_ABBREVIATED_OPTIONS=false \
+	test-tool parse-options --alias 123 >output &&
+	grep "^string: 123" output
+'
+
 cat >typo.err <<\EOF
 error: did you mean `--boolean` (with two dashes ?)
 EOF
diff --git a/t/t2018-checkout-branch.sh b/t/t2018-checkout-branch.sh
index c5014ad9a6..822381dd9d 100755
--- a/t/t2018-checkout-branch.sh
+++ b/t/t2018-checkout-branch.sh
@@ -60,38 +60,47 @@ test_expect_success 'setup' '
 '
 
 test_expect_success 'checkout -b to a new branch, set to HEAD' '
+	test_when_finished "
+		git checkout branch1 &&
+		test_might_fail git branch -D branch2" &&
 	do_checkout branch2
 '
 
-test_expect_success 'checkout -b to a new branch, set to an explicit ref' '
-	git checkout branch1 &&
-	git branch -D branch2 &&
+test_expect_success 'checkout -b to a merge base' '
+	test_when_finished "
+		git checkout branch1 &&
+		test_might_fail git branch -D branch2" &&
+	git checkout -b branch2 branch1...
+'
 
+test_expect_success 'checkout -b to a new branch, set to an explicit ref' '
+	test_when_finished "
+		git checkout branch1 &&
+		test_might_fail git branch -D branch2" &&
 	do_checkout branch2 $HEAD1
 '
 
 test_expect_success 'checkout -b to a new branch with unmergeable changes fails' '
-	git checkout branch1 &&
-
-	# clean up from previous test
-	git branch -D branch2 &&
-
 	setup_dirty_unmergeable &&
 	test_must_fail do_checkout branch2 $HEAD1 &&
 	test_dirty_unmergeable
 '
 
 test_expect_success 'checkout -f -b to a new branch with unmergeable changes discards changes' '
+	test_when_finished "
+		git checkout branch1 &&
+		test_might_fail git branch -D branch2" &&
+
 	# still dirty and on branch1
 	do_checkout branch2 $HEAD1 "-f -b" &&
 	test_must_fail test_dirty_unmergeable
 '
 
 test_expect_success 'checkout -b to a new branch preserves mergeable changes' '
-	git checkout branch1 &&
-
-	# clean up from previous test
-	git branch -D branch2 &&
+	test_when_finished "
+		git reset --hard &&
+		git checkout branch1 &&
+		test_might_fail git branch -D branch2" &&
 
 	setup_dirty_mergeable &&
 	do_checkout branch2 $HEAD1 &&
@@ -99,27 +108,18 @@ test_expect_success 'checkout -b to a new branch preserves mergeable changes' '
 '
 
 test_expect_success 'checkout -f -b to a new branch with mergeable changes discards changes' '
-	# clean up from previous test
-	git reset --hard &&
-
-	git checkout branch1 &&
-
-	# clean up from previous test
-	git branch -D branch2 &&
-
+	test_when_finished git reset --hard HEAD &&
 	setup_dirty_mergeable &&
 	do_checkout branch2 $HEAD1 "-f -b" &&
 	test_must_fail test_dirty_mergeable
 '
 
 test_expect_success 'checkout -b to an existing branch fails' '
-	git reset --hard HEAD &&
-
+	test_when_finished git reset --hard HEAD &&
 	test_must_fail do_checkout branch2 $HEAD2
 '
 
 test_expect_success 'checkout -b to @{-1} fails with the right branch name' '
-	git reset --hard HEAD &&
 	git checkout branch1 &&
 	git checkout branch2 &&
 	echo  >expect "fatal: A branch named '\''branch1'\'' already exists." &&
@@ -133,6 +133,12 @@ test_expect_success 'checkout -B to an existing branch resets branch to HEAD' '
 	do_checkout branch2 "" -B
 '
 
+test_expect_success 'checkout -B to a merge base' '
+	git checkout branch1 &&
+
+	git checkout -B branch2 branch1...
+'
+
 test_expect_success 'checkout -B to an existing branch from detached HEAD resets branch to HEAD' '
 	git checkout $(git rev-parse --verify HEAD) &&
 
@@ -160,6 +166,7 @@ test_expect_success 'checkout -f -B to an existing branch with unmergeable chang
 '
 
 test_expect_success 'checkout -B to an existing branch preserves mergeable changes' '
+	test_when_finished git reset --hard &&
 	git checkout branch1 &&
 
 	setup_dirty_mergeable &&
@@ -168,9 +175,6 @@ test_expect_success 'checkout -B to an existing branch preserves mergeable chang
 '
 
 test_expect_success 'checkout -f -B to an existing branch with mergeable changes discards changes' '
-	# clean up from previous test
-	git reset --hard &&
-
 	git checkout branch1 &&
 
 	setup_dirty_mergeable &&
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index e9ad50b66d..e9d7084d19 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -42,6 +42,10 @@ test_expect_success 'git branch a/b/c should create a branch' '
 	git branch a/b/c && test_path_is_file .git/refs/heads/a/b/c
 '
 
+test_expect_success 'git branch mb master... should create a branch' '
+	git branch mb master... && test_path_is_file .git/refs/heads/mb
+'
+
 test_expect_success 'git branch HEAD should fail' '
 	test_must_fail git branch HEAD
 '
@@ -316,8 +320,8 @@ test_expect_success 'git branch --list -v with --abbrev' '
 test_expect_success 'git branch --column' '
 	COLUMNS=81 git branch --column=column >actual &&
 	cat >expected <<\EOF &&
-  a/b/c     bam       foo       l       * master    n         o/p       r
-  abc       bar       j/k       m/m       master2   o/o       q
+  a/b/c     bam       foo       l       * master    mb        o/o       q
+  abc       bar       j/k       m/m       master2   n         o/p       r
 EOF
 	test_cmp expected actual
 '
@@ -339,6 +343,7 @@ test_expect_success 'git branch --column with an extremely long branch name' '
   m/m
 * master
   master2
+  mb
   n
   o/o
   o/p
@@ -356,8 +361,8 @@ test_expect_success 'git branch with column.*' '
 	git config --unset column.branch &&
 	git config --unset column.ui &&
 	cat >expected <<\EOF &&
-  a/b/c   bam   foo   l   * master    n     o/p   r
-  abc     bar   j/k   m/m   master2   o/o   q
+  a/b/c   bam   foo   l   * master    mb   o/o   q
+  abc     bar   j/k   m/m   master2   n    o/p   r
 EOF
 	test_cmp expected actual
 '
@@ -381,6 +386,7 @@ test_expect_success 'git branch -v with column.ui ignored' '
   m/m
 * master
   master2
+  mb
   n
   o/o
   o/p
diff --git a/t/t4253-am-keep-cr-dos.sh b/t/t4253-am-keep-cr-dos.sh
index 553fe3e88e..6e1b73ec3a 100755
--- a/t/t4253-am-keep-cr-dos.sh
+++ b/t/t4253-am-keep-cr-dos.sh
@@ -51,14 +51,16 @@ test_expect_success 'am with dos files without --keep-cr' '
 
 test_expect_success 'am with dos files with --keep-cr' '
 	git checkout -b dosfiles-keep-cr initial &&
-	git format-patch -k --stdout initial..master | git am --keep-cr -k -3 &&
+	git format-patch -k --stdout initial..master >output &&
+	git am --keep-cr -k -3 output &&
 	git diff --exit-code master
 '
 
 test_expect_success 'am with dos files config am.keepcr' '
 	git config am.keepcr 1 &&
 	git checkout -b dosfiles-conf-keepcr initial &&
-	git format-patch -k --stdout initial..master | git am -k -3 &&
+	git format-patch -k --stdout initial..master >output &&
+	git am -k -3 output &&
 	git diff --exit-code master
 '
 
diff --git a/t/t5580-clone-push-unc.sh b/t/t5580-clone-push-unc.sh
index 217adf3a63..b3c8a92450 100755
--- a/t/t5580-clone-push-unc.sh
+++ b/t/t5580-clone-push-unc.sh
@@ -62,4 +62,16 @@ test_expect_success MINGW 'remote nick cannot contain backslashes' '
 	test_i18ngrep ! "unable to access" err
 '
 
+test_expect_success 'unc alternates' '
+	tree="$(git rev-parse HEAD:)" &&
+	mkdir test-unc-alternate &&
+	(
+		cd test-unc-alternate &&
+		git init &&
+		test_must_fail git show $tree &&
+		echo "$UNCPATH/.git/objects" >.git/objects/info/alternates &&
+		git show $tree
+	)
+'
+
 test_done
diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
index 7411bf7fec..515c6735e9 100755
--- a/t/t6500-gc.sh
+++ b/t/t6500-gc.sh
@@ -181,7 +181,15 @@ test_expect_success 'background auto gc respects lock for all operations' '
 	# now fake a concurrent gc that holds the lock; we can use our
 	# shell pid so that it looks valid.
 	hostname=$(hostname || echo unknown) &&
-	printf "$$ %s" "$hostname" >.git/gc.pid &&
+	shell_pid=$$ &&
+	if test_have_prereq MINGW && test -f /proc/$shell_pid/winpid
+	then
+		# In Git for Windows, Bash (actually, the MSYS2 runtime) has a
+		# different idea of PIDs than git.exe (actually Windows). Use
+		# the Windows PID in this case.
+		shell_pid=$(cat /proc/$shell_pid/winpid)
+	fi &&
+	printf "%d %s" "$shell_pid" "$hostname" >.git/gc.pid &&
 
 	# our gc should exit zero without doing anything
 	run_and_wait_for_auto_gc &&
diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index e285686662..6aeeb279a0 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1702,7 +1702,7 @@ test_expect_success '--points-at finds annotated tags of tags' '
 
 test_expect_success 'recursive tagging should give advice' '
 	sed -e "s/|$//" <<-EOF >expect &&
-	hint: You have created a nested tag. The object referred to by your new is
+	hint: You have created a nested tag. The object referred to by your new tag is
 	hint: already a tag. If you meant to tag the object that it points to, use:
 	hint: |
 	hint: 	git tag -f nested annotated-v4.0^{}
diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
index 3e0a61db23..81a375fa0f 100755
--- a/t/t7519-status-fsmonitor.sh
+++ b/t/t7519-status-fsmonitor.sh
@@ -346,4 +346,12 @@ test_expect_success UNTRACKED_CACHE 'ignore .git changes when invalidating UNTR'
 	test_cmp before after
 '
 
+test_expect_success 'discard_index() also discards fsmonitor info' '
+	test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
+	test_might_fail git update-index --refresh &&
+	test-tool read-cache --print-and-refresh=tracked 2 >actual &&
+	printf "tracked is%s up to date\n" "" " not" >expect &&
+	test_cmp expect actual
+'
+
 test_done
diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
index a9fb971615..5b61c10a9c 100755
--- a/t/t7610-mergetool.sh
+++ b/t/t7610-mergetool.sh
@@ -130,14 +130,55 @@ test_expect_success 'custom mergetool' '
 	test_when_finished "git reset --hard" &&
 	git checkout -b test$test_count branch1 &&
 	git submodule update -N &&
-	test_must_fail git merge master >/dev/null 2>&1 &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
+	test_must_fail git merge master &&
+	( yes "" | git mergetool both ) &&
 	( yes "" | git mergetool file1 file1 ) &&
-	( yes "" | git mergetool file2 "spaced name" >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file12 >/dev/null 2>&1 ) &&
-	( yes "l" | git mergetool submod >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file2 "spaced name" ) &&
+	( yes "" | git mergetool subdir/file3 ) &&
+	( yes "d" | git mergetool file11 ) &&
+	( yes "d" | git mergetool file12 ) &&
+	( yes "l" | git mergetool submod ) &&
+	test "$(cat file1)" = "master updated" &&
+	test "$(cat file2)" = "master new" &&
+	test "$(cat subdir/file3)" = "master new sub" &&
+	test "$(cat submod/bar)" = "branch1 submodule" &&
+	git commit -m "branch1 resolved with mergetool"
+'
+
+test_expect_success 'gui mergetool' '
+	test_config merge.guitool myguitool &&
+	test_config mergetool.myguitool.cmd "(printf \"gui \" && cat \"\$REMOTE\") >\"\$MERGED\"" &&
+	test_config mergetool.myguitool.trustExitCode true &&
+	test_when_finished "git reset --hard" &&
+	git checkout -b test$test_count branch1 &&
+	git submodule update -N &&
+	test_must_fail git merge master &&
+	( yes "" | git mergetool --gui both ) &&
+	( yes "" | git mergetool -g file1 file1 ) &&
+	( yes "" | git mergetool --gui file2 "spaced name" ) &&
+	( yes "" | git mergetool --gui subdir/file3 ) &&
+	( yes "d" | git mergetool --gui file11 ) &&
+	( yes "d" | git mergetool --gui file12 ) &&
+	( yes "l" | git mergetool --gui submod ) &&
+	test "$(cat file1)" = "gui master updated" &&
+	test "$(cat file2)" = "gui master new" &&
+	test "$(cat subdir/file3)" = "gui master new sub" &&
+	test "$(cat submod/bar)" = "branch1 submodule" &&
+	git commit -m "branch1 resolved with mergetool"
+'
+
+test_expect_success 'gui mergetool without merge.guitool set falls back to merge.tool' '
+	test_when_finished "git reset --hard" &&
+	git checkout -b test$test_count branch1 &&
+	git submodule update -N &&
+	test_must_fail git merge master &&
+	( yes "" | git mergetool --gui both ) &&
+	( yes "" | git mergetool -g file1 file1 ) &&
+	( yes "" | git mergetool --gui file2 "spaced name" ) &&
+	( yes "" | git mergetool --gui subdir/file3 ) &&
+	( yes "d" | git mergetool --gui file11 ) &&
+	( yes "d" | git mergetool --gui file12 ) &&
+	( yes "l" | git mergetool --gui submod ) &&
 	test "$(cat file1)" = "master updated" &&
 	test "$(cat file2)" = "master new" &&
 	test "$(cat subdir/file3)" = "master new sub" &&
@@ -153,15 +194,15 @@ test_expect_success 'mergetool crlf' '
 	# test_when_finished is LIFO.)
 	test_config core.autocrlf true &&
 	git checkout -b test$test_count branch1 &&
-	test_must_fail git merge master >/dev/null 2>&1 &&
-	( yes "" | git mergetool file1 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool file2 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool "spaced name" >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file12 >/dev/null 2>&1 ) &&
-	( yes "r" | git mergetool submod >/dev/null 2>&1 ) &&
+	test_must_fail git merge master &&
+	( yes "" | git mergetool file1 ) &&
+	( yes "" | git mergetool file2 ) &&
+	( yes "" | git mergetool "spaced name" ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "" | git mergetool subdir/file3 ) &&
+	( yes "d" | git mergetool file11 ) &&
+	( yes "d" | git mergetool file12 ) &&
+	( yes "r" | git mergetool submod ) &&
 	test "$(printf x | cat file1 -)" = "$(printf "master updated\r\nx")" &&
 	test "$(printf x | cat file2 -)" = "$(printf "master new\r\nx")" &&
 	test "$(printf x | cat subdir/file3 -)" = "$(printf "master new sub\r\nx")" &&
@@ -176,8 +217,8 @@ test_expect_success 'mergetool in subdir' '
 	git submodule update -N &&
 	(
 		cd subdir &&
-		test_must_fail git merge master >/dev/null 2>&1 &&
-		( yes "" | git mergetool file3 >/dev/null 2>&1 ) &&
+		test_must_fail git merge master &&
+		( yes "" | git mergetool file3 ) &&
 		test "$(cat file3)" = "master new sub"
 	)
 '
@@ -188,14 +229,14 @@ test_expect_success 'mergetool on file in parent dir' '
 	git submodule update -N &&
 	(
 		cd subdir &&
-		test_must_fail git merge master >/dev/null 2>&1 &&
-		( yes "" | git mergetool file3 >/dev/null 2>&1 ) &&
-		( yes "" | git mergetool ../file1 >/dev/null 2>&1 ) &&
-		( yes "" | git mergetool ../file2 ../spaced\ name >/dev/null 2>&1 ) &&
-		( yes "" | git mergetool ../both >/dev/null 2>&1 ) &&
-		( yes "d" | git mergetool ../file11 >/dev/null 2>&1 ) &&
-		( yes "d" | git mergetool ../file12 >/dev/null 2>&1 ) &&
-		( yes "l" | git mergetool ../submod >/dev/null 2>&1 ) &&
+		test_must_fail git merge master &&
+		( yes "" | git mergetool file3 ) &&
+		( yes "" | git mergetool ../file1 ) &&
+		( yes "" | git mergetool ../file2 ../spaced\ name ) &&
+		( yes "" | git mergetool ../both ) &&
+		( yes "d" | git mergetool ../file11 ) &&
+		( yes "d" | git mergetool ../file12 ) &&
+		( yes "l" | git mergetool ../submod ) &&
 		test "$(cat ../file1)" = "master updated" &&
 		test "$(cat ../file2)" = "master new" &&
 		test "$(cat ../submod/bar)" = "branch1 submodule" &&
@@ -209,9 +250,9 @@ test_expect_success 'mergetool skips autoresolved' '
 	git submodule update -N &&
 	test_must_fail git merge master &&
 	test -n "$(git ls-files -u)" &&
-	( yes "d" | git mergetool file11 >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file12 >/dev/null 2>&1 ) &&
-	( yes "l" | git mergetool submod >/dev/null 2>&1 ) &&
+	( yes "d" | git mergetool file11 ) &&
+	( yes "d" | git mergetool file12 ) &&
+	( yes "l" | git mergetool submod ) &&
 	output="$(git mergetool --no-prompt)" &&
 	test "$output" = "No files need merging"
 '
@@ -259,9 +300,9 @@ test_expect_success 'mergetool skips resolved paths when rerere is active' '
 	rm -rf .git/rr-cache &&
 	git checkout -b test$test_count branch1 &&
 	git submodule update -N &&
-	test_must_fail git merge master >/dev/null 2>&1 &&
-	( yes "l" | git mergetool --no-prompt submod >/dev/null 2>&1 ) &&
-	( yes "d" "d" | git mergetool --no-prompt >/dev/null 2>&1 ) &&
+	test_must_fail git merge master &&
+	( yes "l" | git mergetool --no-prompt submod ) &&
+	( yes "d" "d" | git mergetool --no-prompt ) &&
 	git submodule update -N &&
 	output="$(yes "n" | git mergetool --no-prompt)" &&
 	test "$output" = "No files need merging"
@@ -369,9 +410,9 @@ test_expect_success 'deleted vs modified submodule' '
 	git checkout -b test$test_count.a test$test_count &&
 	test_must_fail git merge master &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "r" | git mergetool submod ) &&
 	rmdir submod && mv submod-movedaside submod &&
 	test "$(cat submod/bar)" = "branch1 submodule" &&
@@ -386,9 +427,9 @@ test_expect_success 'deleted vs modified submodule' '
 	git submodule update -N &&
 	test_must_fail git merge master &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "l" | git mergetool submod ) &&
 	test ! -e submod &&
 	output="$(git mergetool --no-prompt)" &&
@@ -400,9 +441,9 @@ test_expect_success 'deleted vs modified submodule' '
 	git submodule update -N &&
 	test_must_fail git merge test$test_count &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "r" | git mergetool submod ) &&
 	test ! -e submod &&
 	test -d submod.orig &&
@@ -416,9 +457,9 @@ test_expect_success 'deleted vs modified submodule' '
 	git submodule update -N &&
 	test_must_fail git merge test$test_count &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "l" | git mergetool submod ) &&
 	test "$(cat submod/bar)" = "master submodule" &&
 	git submodule update -N &&
@@ -440,9 +481,9 @@ test_expect_success 'file vs modified submodule' '
 	git checkout -b test$test_count.a branch1 &&
 	test_must_fail git merge master &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "r" | git mergetool submod ) &&
 	rmdir submod && mv submod-movedaside submod &&
 	test "$(cat submod/bar)" = "branch1 submodule" &&
@@ -456,9 +497,9 @@ test_expect_success 'file vs modified submodule' '
 	git checkout -b test$test_count.b test$test_count &&
 	test_must_fail git merge master &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "l" | git mergetool submod ) &&
 	git submodule update -N &&
 	test "$(cat submod)" = "not a submodule" &&
@@ -472,9 +513,9 @@ test_expect_success 'file vs modified submodule' '
 	git submodule update -N &&
 	test_must_fail git merge test$test_count &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both >/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "r" | git mergetool submod ) &&
 	test -d submod.orig &&
 	git submodule update -N &&
@@ -488,9 +529,9 @@ test_expect_success 'file vs modified submodule' '
 	git submodule update -N &&
 	test_must_fail git merge test$test_count &&
 	test -n "$(git ls-files -u)" &&
-	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 >/dev/null 2>&1 ) &&
-	( yes "" | git mergetool both>/dev/null 2>&1 ) &&
-	( yes "d" | git mergetool file11 file12 >/dev/null 2>&1 ) &&
+	( yes "" | git mergetool file1 file2 spaced\ name subdir/file3 ) &&
+	( yes "" | git mergetool both ) &&
+	( yes "d" | git mergetool file11 file12 ) &&
 	( yes "l" | git mergetool submod ) &&
 	test "$(cat submod/bar)" = "master submodule" &&
 	git submodule update -N &&
@@ -543,7 +584,7 @@ test_expect_success 'submodule in subdirectory' '
 	git add subdir/subdir_module &&
 	git commit -m "change submodule in subdirectory on test$test_count.b" &&
 
-	test_must_fail git merge test$test_count.a >/dev/null 2>&1 &&
+	test_must_fail git merge test$test_count.a &&
 	(
 		cd subdir &&
 		( yes "l" | git mergetool subdir_module )
@@ -554,7 +595,7 @@ test_expect_success 'submodule in subdirectory' '
 	git reset --hard &&
 	git submodule update -N &&
 
-	test_must_fail git merge test$test_count.a >/dev/null 2>&1 &&
+	test_must_fail git merge test$test_count.a &&
 	( yes "r" | git mergetool subdir/subdir_module ) &&
 	test "$(cat subdir/subdir_module/file15)" = "test$test_count.b" &&
 	git submodule update -N &&
@@ -641,7 +682,7 @@ test_expect_success 'filenames seen by tools start with ./' '
 	test_config mergetool.myecho.trustExitCode true &&
 	test_must_fail git merge master &&
 	git mergetool --no-prompt --tool myecho -- both >actual &&
-	grep ^\./both_LOCAL_ actual >/dev/null
+	grep ^\./both_LOCAL_ actual
 '
 
 test_lazy_prereq MKTEMP '
@@ -658,8 +699,8 @@ test_expect_success MKTEMP 'temporary filenames are used with mergetool.writeToT
 	test_config mergetool.myecho.trustExitCode true &&
 	test_must_fail git merge master &&
 	git mergetool --no-prompt --tool myecho -- both >actual &&
-	! grep ^\./both_LOCAL_ actual >/dev/null &&
-	grep /both_LOCAL_ actual >/dev/null
+	! grep ^\./both_LOCAL_ actual &&
+	grep /both_LOCAL_ actual
 '
 
 test_expect_success 'diff.orderFile configuration is honored' '
diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index 480dd0633f..6bac9ed180 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -279,11 +279,27 @@ test_expect_success 'difftool + mergetool config variables' '
 	echo branch >expect &&
 	git difftool --no-prompt branch >actual &&
 	test_cmp expect actual &&
+	git difftool --gui --no-prompt branch >actual &&
+	test_cmp expect actual &&
 
 	# set merge.tool to something bogus, diff.tool to test-tool
 	test_config merge.tool bogus-tool &&
 	test_config diff.tool test-tool &&
 	git difftool --no-prompt branch >actual &&
+	test_cmp expect actual &&
+	git difftool --gui --no-prompt branch >actual &&
+	test_cmp expect actual &&
+
+	# set merge.tool, diff.tool to something bogus, merge.guitool to test-tool
+	test_config diff.tool bogus-tool &&
+	test_config merge.guitool test-tool &&
+	git difftool --gui --no-prompt branch >actual &&
+	test_cmp expect actual &&
+
+	# set merge.tool, diff.tool, merge.guitool to something bogus, diff.guitool to test-tool
+	test_config merge.guitool bogus-tool &&
+	test_config diff.guitool test-tool &&
+	git difftool --gui --no-prompt branch >actual &&
 	test_cmp expect actual
 '
 
@@ -715,4 +731,12 @@ test_expect_success 'outside worktree' '
 	test_cmp expect actual
 '
 
+test_expect_success 'difftool --gui, --tool and --extcmd are mutually exclusive' '
+	difftool_test_setup &&
+	test_must_fail git difftool --gui --tool=test-tool &&
+	test_must_fail git difftool --gui --extcmd=cat &&
+	test_must_fail git difftool --tool=test-tool --extcmd=cat &&
+	test_must_fail git difftool --gui --tool=test-tool --extcmd=cat
+'
+
 test_done
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 908ddb9c46..599fd70e14 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1522,7 +1522,7 @@ test_lazy_prereq NOT_ROOT '
 '
 
 test_lazy_prereq JGIT '
-	type jgit
+	jgit --version
 '
 
 # SANITY is about "can you correctly predict what the filesystem would