Teach git-p4 to ignore case in perforce filenames if configured.

When files are added to perforce, the path to that file has whichever case
configuration that exists on the machine of the user who added the file.
What does that mean? It means that when Alice adds a file

//depot/DirA/FileA.txt

... and Bob adds:

//depot/dirA/FileB.txt

... we may or may not get a problem. If a user sets the config variable
git-p4.ignorecase to "true", we will consider //depot/DirA and //depot/dirA
to be the same directory.

Signed-off-by: Tor Arvid Lund <torarvid@gmail.com>
Acked-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -456,6 +456,19 @@ def p4ChangesForPaths(depotPaths, changeRange):
     changelist.sort()
     return changelist
 
+def p4PathStartsWith(path, prefix):
+    # This method tries to remedy a potential mixed-case issue:
+    #
+    # If UserA adds  //depot/DirA/file1
+    # and UserB adds //depot/dira/file2
+    #
+    # we may or may not have a problem. If you have core.ignorecase=true,
+    # we treat DirA and dira as the same directory
+    ignorecase = gitConfig("core.ignorecase", "--bool") == "true"
+    if ignorecase:
+        return path.lower().startswith(prefix.lower())
+    return path.startswith(prefix)
+
 class Command:
     def __init__(self):
         self.usage = "usage: %prog [options]"
@@ -603,7 +616,7 @@ class P4Submit(Command):
                     lastTab = path.rfind("\t")
                     if lastTab != -1:
                         path = path[:lastTab]
-                        if not path.startswith(self.depotPath):
+                        if not p4PathStartsWith(path, self.depotPath):
                             continue
                 else:
                     inFilesSection = False
@@ -941,11 +954,11 @@ class P4Sync(Command):
             path =  commit["depotFile%s" % fnum]
 
             if [p for p in self.cloneExclude
-                if path.startswith (p)]:
+                if p4PathStartsWith(path, p)]:
                 found = False
             else:
                 found = [p for p in self.depotPaths
-                         if path.startswith (p)]
+                         if p4PathStartsWith(path, p)]
             if not found:
                 fnum = fnum + 1
                 continue
@@ -980,7 +993,7 @@ class P4Sync(Command):
             prefixes = [re.sub("^(//[^/]+/).*", r'\1', prefixes[0])]
 
         for p in prefixes:
-            if path.startswith(p):
+            if p4PathStartsWith(path, p):
                 path = path[len(p):]
 
         return path
@@ -991,7 +1004,7 @@ class P4Sync(Command):
         while commit.has_key("depotFile%s" % fnum):
             path =  commit["depotFile%s" % fnum]
             found = [p for p in self.depotPaths
-                     if path.startswith (p)]
+                     if p4PathStartsWith(path, p)]
             if not found:
                 fnum = fnum + 1
                 continue
@@ -1144,7 +1157,7 @@ class P4Sync(Command):
         # create a commit.
         new_files = []
         for f in files:
-            if [p for p in branchPrefixes if f['path'].startswith(p)]:
+            if [p for p in branchPrefixes if p4PathStartsWith(f['path'], p)]:
                 new_files.append (f)
             else:
                 sys.stderr.write("Ignoring file outside of prefix: %s\n" % path)
@@ -1308,7 +1321,7 @@ class P4Sync(Command):
                 source = paths[0]
                 destination = paths[1]
                 ## HACK
-                if source.startswith(self.depotPaths[0]) and destination.startswith(self.depotPaths[0]):
+                if p4PathStartsWith(source, self.depotPaths[0]) and p4PathStartsWith(destination, self.depotPaths[0]):
                     source = source[len(self.depotPaths[0]):-4]
                     destination = destination[len(self.depotPaths[0]):-4]