git p4: refactor diffOpts calculation

P4Submit.applyCommit()

To avoid recalculating the same diffOpts for each commit, move it
out of applyCommit() and into the top-level run().  Also fix a bug
in that code which interpreted the value of detectRenames as a
string rather than as a boolean.

[pw: fix documentation, rearrange code a bit]

Signed-off-by: Gary Gibbons <ggibbons@perforce.com>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-p4.py

@@ -1046,27 +1046,8 @@ class P4Submit(Command, P4UserMap):
 
         (p4User, gitEmail) = self.p4UserForCommit(id)
 
-        if not self.detectRenames:
-            # If not explicitly set check the config variable
-            self.detectRenames = gitConfig("git-p4.detectRenames")
 
-        if self.detectRenames.lower() == "false" or self.detectRenames == "":
-            diffOpts = ""
-        elif self.detectRenames.lower() == "true":
-            diffOpts = "-M"
-        else:
-            diffOpts = "-M%s" % self.detectRenames
-
-        detectCopies = gitConfig("git-p4.detectCopies")
-        if detectCopies.lower() == "true":
-            diffOpts += " -C"
-        elif detectCopies != "" and detectCopies.lower() != "false":
-            diffOpts += " -C%s" % detectCopies
-
-        if gitConfig("git-p4.detectCopiesHarder", "--bool") == "true":
-            diffOpts += " --find-copies-harder"
-
-        diff = read_pipe_lines("git diff-tree -r %s \"%s^\" \"%s\"" % (diffOpts, id, id))
+        diff = read_pipe_lines("git diff-tree -r %s \"%s^\" \"%s\"" % (self.diffOpts, id, id))
         filesToAdd = set()
         filesToDelete = set()
         editedFiles = set()
@@ -1433,6 +1414,37 @@ class P4Submit(Command, P4UserMap):
         if self.preserveUser:
             self.checkValidP4Users(commits)
 
+        #
+        # Build up a set of options to be passed to diff when
+        # submitting each commit to p4.
+        #
+        if self.detectRenames:
+            # command-line -M arg
+            self.diffOpts = "-M"
+        else:
+            # If not explicitly set check the config variable
+            detectRenames = gitConfig("git-p4.detectRenames")
+
+            if detectRenames.lower() == "false" or detectRenames == "":
+                self.diffOpts = ""
+            elif detectRenames.lower() == "true":
+                self.diffOpts = "-M"
+            else:
+                self.diffOpts = "-M%s" % detectRenames
+
+        # no command-line arg for -C or --find-copies-harder, just
+        # config variables
+        detectCopies = gitConfig("git-p4.detectCopies")
+        if detectCopies.lower() == "false" or detectCopies == "":
+            pass
+        elif detectCopies.lower() == "true":
+            self.diffOpts += " -C"
+        else:
+            self.diffOpts += " -C%s" % detectCopies
+
+        if gitConfig("git-p4.detectCopiesHarder", "--bool") == "true":
+            self.diffOpts += " --find-copies-harder"
+
         while len(commits) > 0:
             commit = commits[0]
             commits = commits[1:]