Merge branch 'prepare-the-test-suite-for-symlink-support-on-windows'

Git for Windows has supported symbolic links for quite some time:
In git-for-windows#156, this support was
introduced already into Git for Windows v2.4.2.windows.1 in May 2015.

However, the Git for Windows CI never ran the test suite with symbolic
link support because the MSYS2 runtime (i.e. the POSIX emulation layer
required to run Git's test suite because the latter is written in Unix
shell script) does not support symbolic links right out of the box. This
is for historical reasons: Symbolic link support was introduced in
Windows 7, but these links could only be created by administrators by
default, and it took until Windows 10 Build 14972 that at least in
Developer Mode, non-administrators would be permitted to create them.

The MSYS2 runtime _does_ have some sort of support for symbolic links,
although with caveats: seeing as it expects the inputs as Unix-like
paths, but the outputs need to be Win32 symbolic links pointing to Win32
paths, some normalization has to be performed in the process. This leads
to sometimes surprising behavior e.g. when a link target like `a/b/..`
is normalized to `a`.

It has been a minute or three since the time when Windows versions
without symbolic link support were common, therefore there are plans to
turn on that support in the MSYS2 runtime on these Windows versions by
default, see msys2/msys2-runtime#114 for more
details about this.

To prepare for this, I am working toward upstreaming Git for Windows'
own support for symbolic links. And to prepare for that, in turn, I am
hereby contributing preemptively the fixes required to eventually let
Git's test suite pass when both MSYS2 runtime and Git support symbolic
links.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

apply.c

@@ -3779,7 +3779,7 @@ static int check_preimage(struct apply_state *state,
 		if (*ce && !(*ce)->ce_mode)
 			BUG("ce_mode == 0 for path '%s'", old_name);
 
-		if (trust_executable_bit)
+		if (trust_executable_bit || !S_ISREG(st->st_mode))
 			st_mode = ce_mode_from_stat(*ce, st->st_mode);
 		else if (*ce)
 			st_mode = (*ce)->ce_mode;

compat/mingw.c

@@ -858,6 +858,7 @@ int mingw_open (const char *filename, int oflags, ...)
 	int fd, create = (oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL);
 	wchar_t wfilename[MAX_LONG_PATH];
 	open_fn_t open_fn;
+	WIN32_FILE_ATTRIBUTE_DATA fdata;
 
 	DECLARE_PROC_ADDR(ntdll.dll, NTSTATUS, NTAPI, RtlGetLastNtStatus, void);
 
@@ -891,6 +892,19 @@ int mingw_open (const char *filename, int oflags, ...)
 	else if (xutftowcs_long_path(wfilename, filename) < 0)
 		return -1;
 
+	/*
+	 * When `symlink` exists and is a symbolic link pointing to a
+	 * non-existing file, `_wopen(symlink, O_CREAT | O_EXCL)` would
+	 * create that file. Not what we want: Linux would say `EEXIST`
+	 * in that instance, which is therefore what Git expects.
+	 */
+	if (create &&
+	    GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata) &&
+	    (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)) {
+		errno = EEXIST;
+		return -1;
+	}
+
 	fd = open_fn(wfilename, oflags, mode);
 
 	/*

t/t0001-init.sh

@@ -425,7 +425,10 @@ test_expect_success SYMLINKS 're-init to move gitdir symlink' '
 	git init --separate-git-dir ../realgitdir
 	) &&
 	echo "gitdir: $(pwd)/realgitdir" >expected &&
-	test_cmp expected newdir/.git &&
+	case "$GIT_TEST_CMP" in
+	*--no-index*) ;; # git diff --no-index does not resolve symlinks
+	*) test_cmp expected newdir/.git;;
+	esac &&
 	test_cmp expected newdir/here &&
 	test_path_is_dir realgitdir/refs
 '

t/t0301-credential-cache.sh

@@ -123,7 +123,8 @@ test_expect_success SYMLINKS 'use user socket if user directory is a symlink to
 		rmdir \"\$HOME/dir/\" &&
 		rm \"\$HOME/.git-credential-cache\"
 	" &&
-	mkdir -p -m 700 "$HOME/dir/" &&
+	mkdir -p "$HOME/dir/" &&
+	chmod 700 "$HOME/dir/" &&
 	ln -s "$HOME/dir" "$HOME/.git-credential-cache" &&
 	check approve cache <<-\EOF &&
 	protocol=https

t/t0600-reffiles-backend.sh

@@ -467,7 +467,7 @@ test_expect_success POSIXPERM 'git reflog expire honors core.sharedRepository' '
 	esac
 '
 
-test_expect_success SYMLINKS 'symref transaction supports symlinks' '
+test_expect_success SYMLINKS,!MINGW 'symref transaction supports symlinks' '
 	test_when_finished "git symbolic-ref -d TEST_SYMREF_HEAD" &&
 	git update-ref refs/heads/new @ &&
 	test_config core.prefersymlinkrefs true &&

t/t1006-cat-file.sh

@@ -1048,18 +1048,28 @@ test_expect_success 'git cat-file --batch-check --follow-symlinks works for out-
 	echo .. >>expect &&
 	echo HEAD:dir/subdir/out-of-repo-link-dir | git cat-file --batch-check --follow-symlinks >actual &&
 	test_cmp expect actual &&
-	echo symlink 3 >expect &&
-	echo ../ >>expect &&
+	if test_have_prereq MINGW,SYMLINKS
+	then
+		test_write_lines "symlink 2" ..
+	else
+		test_write_lines "symlink 3" ../
+	fi >expect &&
 	echo HEAD:dir/subdir/out-of-repo-link-dir-trailing | git cat-file --batch-check --follow-symlinks >actual &&
 	test_cmp expect actual
 '
 
 test_expect_success 'git cat-file --batch-check --follow-symlinks works for symlinks with internal ..' '
-	echo HEAD: | git cat-file --batch-check >expect &&
-	echo HEAD:up-down | git cat-file --batch-check --follow-symlinks >actual &&
-	test_cmp expect actual &&
-	echo HEAD:up-down-trailing | git cat-file --batch-check --follow-symlinks >actual &&
-	test_cmp expect actual &&
+	if test_have_prereq !MINGW
+	then
+		# The `up-down` and `up-down-trailing` symlinks are normalized
+		# in MSYS in `winsymlinks` mode and are therefore in a
+		# different shape than Git expects them.
+		echo HEAD: | git cat-file --batch-check >expect &&
+		echo HEAD:up-down | git cat-file --batch-check --follow-symlinks >actual &&
+		test_cmp expect actual &&
+		echo HEAD:up-down-trailing | git cat-file --batch-check --follow-symlinks >actual &&
+		test_cmp expect actual
+	fi &&
 	echo HEAD:up-down-file | git cat-file --batch-check --follow-symlinks >actual &&
 	test_cmp found actual &&
 	echo symlink 7 >expect &&

t/t1305-config-include.sh

@@ -286,7 +286,7 @@ test_expect_success SYMLINKS 'conditional include, relative path with symlinks'
 	)
 '
 
-test_expect_success SYMLINKS 'conditional include, gitdir matching symlink' '
+test_expect_success SYMLINKS,!MINGW 'conditional include, gitdir matching symlink' '
 	ln -s foo bar &&
 	(
 		cd bar &&
@@ -298,7 +298,7 @@ test_expect_success SYMLINKS 'conditional include, gitdir matching symlink' '
 	)
 '
 
-test_expect_success SYMLINKS 'conditional include, gitdir matching symlink, icase' '
+test_expect_success SYMLINKS,!MINGW 'conditional include, gitdir matching symlink, icase' '
 	(
 		cd bar &&
 		echo "[includeIf \"gitdir/i:BAR/\"]path=bar8" >>.git/config &&

t/t6423-merge-rename-directories.sh

@@ -5158,7 +5158,12 @@ test_setup_12m () {
 		git switch B &&
 		git rm dir/subdir/file &&
 		mkdir dir &&
-		ln -s /dev/null dir/subdir &&
+		if test_have_prereq MINGW
+		then
+			cmd //c 'mklink dir\subdir NUL'
+		else
+			ln -s /dev/null dir/subdir
+		fi &&
 		git add . &&
 		git commit -m "B"
 	)

t/t7800-difftool.sh

@@ -752,11 +752,11 @@ test_expect_success SYMLINKS 'difftool --dir-diff handles modified symlinks' '
 		c
 	EOF
 	git difftool --symlinks --dir-diff --extcmd ls >output &&
-	grep -v ^/ output >actual &&
+	grep -v ":\$" output >actual &&
 	test_cmp expect actual &&
 
 	git difftool --no-symlinks --dir-diff --extcmd ls >output &&
-	grep -v ^/ output >actual &&
+	grep -v ":\$" output >actual &&
 	test_cmp expect actual &&
 
 	# The left side contains symlink "c" that points to "b"
@@ -786,11 +786,11 @@ test_expect_success SYMLINKS 'difftool --dir-diff handles modified symlinks' '
 
 	EOF
 	git difftool --symlinks --dir-diff --extcmd ls >output &&
-	grep -v ^/ output >actual &&
+	grep -v ":\$" output >actual &&
 	test_cmp expect actual &&
 
 	git difftool --no-symlinks --dir-diff --extcmd ls >output &&
-	grep -v ^/ output >actual &&
+	grep -v ":\$" output >actual &&
 	test_cmp expect actual
 '
 

t/t9700/test.pl

@@ -117,7 +117,12 @@ sub adjust_dirsep {
 unlink $tmpfile;
 
 # paths
-is($r->repo_path, $abs_repo_dir . "/.git", "repo_path");
+my $abs_git_dir = $abs_repo_dir . "/.git";
+if ($^O eq 'msys' or $^O eq 'cygwin') {
+  $abs_git_dir = `cygpath -am "$abs_repo_dir/.git"`;
+  $abs_git_dir =~ s/\r?\n?$//;
+}
+is($r->repo_path, $abs_git_dir, "repo_path");
 is($r->wc_path, $abs_repo_dir . "/", "wc_path");
 is($r->wc_subdir, "", "wc_subdir initial");
 $r->wc_chdir("directory1");
@@ -127,7 +132,7 @@ sub adjust_dirsep {
 # Object generation in sub directory
 chdir("directory2");
 my $r2 = Git->repository();
-is($r2->repo_path, $abs_repo_dir . "/.git", "repo_path (2)");
+is($r2->repo_path, $abs_git_dir, "repo_path (2)");
 is($r2->wc_path, $abs_repo_dir . "/", "wc_path (2)");
 is($r2->wc_subdir, "directory2/", "wc_subdir initial (2)");