fixup! Add functionality for converting UNIX paths in arguments and e…

…nvironment variables to Windows form for native Win32 applications.

When we fixed MSYS2's automatic Unix <-> Windows path conversion to
identify and skip Git-style `<rev>:<path>` arguments (and incidentally
also scp-style `<host>:<path>` ones), we assumed that path lists
containing relative paths would be a rare scenario.

My, was this assumption wrong!

Let's add another heuristic that detects absolute paths at the beginning
of path lists, and relative ones starting with either `./` or `../`,
neither of which match those Git-style nor scp-style arguments, and then
prevent the detection of the latter style from kicking in.

This addresses msys2#208

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

winsup/cygwin/msys2_path_conv.cc

@@ -358,6 +358,18 @@ path_type find_path_start_and_type(const char** src, int recurse, const char* en
         return NONE;
     }
 
+    /*
+     * Discern between Git's `<rev>:<path>`, SCP's `<host>:<path>` pattern
+     * (which is not a path list but may naïvely look like one) on the one
+     * hand, and path lists starting with `/<path>`, `./<path>` or `../<path>`
+     * on the other hand.
+     */
+    bool potential_path_list = *it == '/' ||
+	    (*it == '.' &&
+		(it[1] == ':' || it[1] == '/' ||
+		 (it[1] == '.' &&
+			(it[2] == ':' || it[2] == '/'))));
+
     /*
      * Prevent Git's :file.txt and :/message syntax from beeing modified.
      */
@@ -383,7 +395,7 @@ path_type find_path_start_and_type(const char** src, int recurse, const char* en
                 goto skip_p2w;
 
             // Leave Git's <rev>:./name syntax alone
-            if (it + 1 < end && it[1] == '.') {
+            if (!potential_path_list && it + 1 < end && it[1] == '.') {
                 if (it + 2 < end && it[2] == '/')
                     goto skip_p2w;
                 if (it + 3 < end && it[2] == '.' && it[3] == '/')