git-p4: honor core.ignorecase when using P4 client specs

Perforce depot may record paths in mixed cases, e.g. "p4 files" may
show that there are these two paths:

   //depot/Path/to/file1
   //depot/pATH/to/file2

and with "p4" or "p4v", these end up in the same directory, e.g.

   //depot/Path/to/file1
   //depot/Path/to/file2

which is the desired outcome on case insensitive systems.

If git-p4 is used with client spec "//depot/Path/...", however, then
all files not matching the case in the client spec are ignored (in
the example above "//depot/pATH/to/file2").

Fix this by using the path case that appears first in lexicographical
order when core.ignorecase is set to true. This behavior is consistent
with "p4" and "p4v".

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Acked-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -1950,10 +1950,14 @@ class View(object):
             if "unmap" in res:
                 # it will list all of them, but only one not unmap-ped
                 continue
+            if gitConfigBool("core.ignorecase"):
+                res['depotFile'] = res['depotFile'].lower()
             self.client_spec_path_cache[res['depotFile']] = self.convert_client_path(res["clientFile"])
 
         # not found files or unmap files set to ""
         for depotFile in fileArgs:
+            if gitConfigBool("core.ignorecase"):
+                depotFile = depotFile.lower()
             if depotFile not in self.client_spec_path_cache:
                 self.client_spec_path_cache[depotFile] = ""
 
@@ -1962,6 +1966,9 @@ class View(object):
            depot file should live.  Returns "" if the file should
            not be mapped in the client."""
 
+        if gitConfigBool("core.ignorecase"):
+            depot_path = depot_path.lower()
+
         if depot_path in self.client_spec_path_cache:
             return self.client_spec_path_cache[depot_path]