patch 9.1.1948: Windows: Vim adds current directory to search path

Problem:  Windows: Vim always adds the current directory to search path.
          This should only happen when using cmd.exe as 'shell'. For
          example, powershell won't run binaries from the current
          directory.
Solution: Only add current directory to system path, when using cmd.exe
          as 'shell'.

related: #10341
related: 083ec6d9a3

Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/builtin.txt

@@ -2716,10 +2716,12 @@ executable({expr})					*executable()*
 		executable is always found.  Since this directory is added to
 		$PATH it should also work to execute it |win32-PATH|.
 					*NoDefaultCurrentDirectoryInExePath*
-		On MS-Windows an executable in Vim's current working directory
+		On MS-Windows when using cmd.exe as 'shell' an executable in
-		is also normally found, but this can be disabled by setting
+		Vim's current working directory is also normally found, which
-		the `$NoDefaultCurrentDirectoryInExePath` environment variable.
+		can be disabled by setting the
-		This is always done for |:!| commands, for security reasons.
+		`$NoDefaultCurrentDirectoryInExePath` environment variable.
+		This is always done when executing external commands using
+		e.g. |:!|, |:make|, |system()| for security reasons.
 
 		The result is a Number:
 			1	exists

src/os_win32.c

@@ -2867,7 +2867,8 @@ executable_exists(
 		goto theend;
 	    }
 
-	    if (mch_getenv("NoDefaultCurrentDirectoryInExePath") == NULL)
+	    if (mch_getenv("NoDefaultCurrentDirectoryInExePath") == NULL &&
+		    strstr((char *)gettail(p_sh), "cmd.exe") != NULL)
 	    {
 		STRCPY(pathbuf.string, ".;");
 		pathbuf.length = 2;

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1948,
 /**/
     1947,
 /**/