Use patch.patch() when checking for patch availability.

The test is closer to what we want to know. It also makes sense when you deal with patched versions of patch() as most people do under win32.

mercurial/commands.py

@@ -891,27 +891,28 b' def debuginstall(ui):'
         # actually attempt a patch here
         a = "1\n2\n3\n4\n"
         b = "1\n2\n3\ninsert\n4\n"
-        d = mdiff.unidiff(a, None, b, None, "a")
         fa = writetemp(a)
+        d = mdiff.unidiff(a, None, b, None, os.path.basename(fa))
         fd = writetemp(d)
-        fp = os.popen('%s %s %s' % (patcher, fa, fd))
-        files = []
-        output = ""
-        for line in fp:
-            output += line
-            if line.startswith('patching file '):
-                pf = util.parse_patch_output(line.rstrip())
-                files.append(pf)
-        if files != [fa]:
+        
+        files = {}
+        try:
+            patch.patch(fd, ui, cwd=os.path.dirname(fa), files=files)
+        except util.Abort, e:
+            ui.write(_(" patch call failed:\n"))
+            ui.write(" " + str(e) + "\n")
+            problems += 1
+        else:            
+            if list(files) != [os.path.basename(fa)]:
             ui.write(_(" unexpected patch output!"))
             ui.write(_(" (you may have an incompatible version of patch)\n"))
-            ui.write(output)
             problems += 1
         a = file(fa).read()
         if a != b:
             ui.write(_(" patch test failed!"))
             ui.write(_(" (you may have an incompatible version of patch)\n"))
             problems += 1
+                
         os.unlink(fa)
         os.unlink(fd)