git-p4: Support purged files and optimize memory usage

Purged files are handled as if they are merely deleted, which is not
entirely optimal, but I don't know of any other way to handle them.
File data is deleted from memory as early as they can, and they are more
efficiently handled, at (significant) cost to CPU usage.

Still need to handle p4 branches with spaces in their names.
Still need to make git-p4 clone more reliable.
 - Perhaps with a --continue option. (Sometimes the p4 server kills
 the connection)
Signed-off-by: NJohn Chapman <thestar@fussycoder.id.au>
Acked-by: NSimon Hausmann <simon@lst.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -946,7 +946,7 @@ class P4Sync(Command):
 
             if includeFile:
                 filesForCommit.append(f)
-                if f['action'] != 'delete':
+                if f['action'] not in ('delete', 'purge'):
                     filesToRead.append(f)
 
         filedata = []
@@ -965,11 +965,11 @@ class P4Sync(Command):
         while j < len(filedata):
             stat = filedata[j]
             j += 1
-            text = [];
+            text = ''
             while j < len(filedata) and filedata[j]['code'] in ('text', 'unicode', 'binary'):
-                text.append(filedata[j]['data'])
+                text += filedata[j]['data']
+                del filedata[j]['data']
                 j += 1
-            text = ''.join(text)
 
             if not stat.has_key('depotFile'):
                 sys.stderr.write("p4 print fails with: %s\n" % repr(stat))
@@ -1038,7 +1038,7 @@ class P4Sync(Command):
                 continue
 
             relPath = self.stripRepoPath(file['path'], branchPrefixes)
-            if file["action"] == "delete":
+            if file["action"] in ("delete", "purge"):
                 self.gitStream.write("D %s\n" % relPath)
             else:
                 data = file['data']
@@ -1077,7 +1077,7 @@ class P4Sync(Command):
 
                 cleanedFiles = {}
                 for info in files:
-                    if info["action"] == "delete":
+                    if info["action"] in ("delete", "purge"):
                         continue
                     cleanedFiles[info["depotFile"]] = info["rev"]
 
@@ -1400,7 +1400,7 @@ class P4Sync(Command):
             if change > newestRevision:
                 newestRevision = change
 
-            if info["action"] == "delete":
+            if info["action"] in ("delete", "purge"):
                 # don't increase the file cnt, otherwise details["depotFile123"] will have gaps!
                 #fileCnt = fileCnt + 1
                 continue