patch 9.1.0567: Cannot use relative paths as findfile() stop directories

Problem:  Cannot use relative paths as findfile() stop directories.
Solution: Change a relative path to an absolute path.
          (zeertzjq)

related: #15200
closes: #15202

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/findfile.c b/src/findfile.c
index 149f7c6..d1cd5f0 100644
--- a/src/findfile.c
+++ b/src/findfile.c
@@ -418,6 +418,7 @@
 	    {
 		char_u	*helper;
 		void	*ptr;
+		size_t	len;
 
 		helper = walker;
 		ptr = vim_realloc(search_ctx->ffsc_stopdirs_v,
@@ -428,18 +429,21 @@
 		    // ignore, keep what we have and continue
 		    break;
 		walker = vim_strchr(walker, ';');
-		if (walker)
+		len = walker ? (size_t)(walker - helper) : STRLEN(helper);
+		// "" means ascent till top of directory tree.
+		if (*helper != NUL && !vim_isAbsName(helper)
+							 && len + 1 < MAXPATHL)
 		{
+		    // Make the stop dir an absolute path name.
+		    vim_strncpy(ff_expand_buffer, helper, len);
 		    search_ctx->ffsc_stopdirs_v[dircount-1] =
-					 vim_strnsave(helper, walker - helper);
-		    walker++;
+					FullName_save(ff_expand_buffer, FALSE);
 		}
 		else
-		    // this might be "", which means ascent till top
-		    // of directory tree.
 		    search_ctx->ffsc_stopdirs_v[dircount-1] =
-							  vim_strsave(helper);
-
+						     vim_strnsave(helper, len);
+		if (walker)
+		    walker++;
 		dircount++;
 
 	    } while (walker != NULL);
diff --git a/src/testdir/test_findfile.vim b/src/testdir/test_findfile.vim
index 89e583a..9247a81 100644
--- a/src/testdir/test_findfile.vim
+++ b/src/testdir/test_findfile.vim
@@ -98,12 +98,25 @@
 
   " Test upwards search with stop-directory.
   cd Xdir2
+  let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2/Xdir3/', -1)
+  call assert_equal(1, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2/Xdir3', -1)
+  call assert_equal(1, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  let l = findfile('bar', ';../', -1)
+  call assert_equal(1, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+
   let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2/', -1)
   call assert_equal(1, len(l))
   call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
   let l = findfile('bar', ';' . save_dir . '/Xfinddir1/Xdir2', -1)
   call assert_equal(1, len(l))
   call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  let l = findfile('bar', ';../../', -1)
+  call assert_equal(1, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
 
   let l = findfile('bar', ';' . save_dir . '/Xfinddir1/', -1)
   call assert_equal(2, len(l))
@@ -113,6 +126,10 @@
   call assert_equal(2, len(l))
   call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
   call assert_match('.*/Xfinddir1/bar',             l[1])
+  let l = findfile('bar', ';../../../', -1)
+  call assert_equal(2, len(l))
+  call assert_match('.*/Xfinddir1/Xdir2/Xdir3/bar', l[0])
+  call assert_match('.*/Xfinddir1/bar',             l[1])
 
   " Test combined downwards and upwards search from Xdir2/.
   cd ../..
diff --git a/src/testdir/test_taglist.vim b/src/testdir/test_taglist.vim
index 136acb3..8e07972 100644
--- a/src/testdir/test_taglist.vim
+++ b/src/testdir/test_taglist.vim
@@ -146,6 +146,15 @@
   let &tags = './Xtags;' .. fnamemodify('./..', ':p')
   call assert_equal(0, len(tagfiles()))
 
+  let &tags = './Xtags;../'
+  call assert_equal(0, len(tagfiles()))
+
+  cd ..
+  call assert_equal(1, len(tagfiles()))
+
+  cd ..
+  call assert_equal(1, len(tagfiles()))
+
   set tags&
   call chdir(save_cwd)
 endfunc
diff --git a/src/version.c b/src/version.c
index 4e14bf1..c7499bb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    567,
+/**/
     566,
 /**/
     565,