[PATCHv1 3/3] git-p4: fixing --changes-block-size handling

[Luke Diamand <luke@diamand.org>]

The --changes-block-size handling was intended to help when
a user has a limited "maxscanrows" (see "p4 group"). It used
"p4 changes -m $maxchanges" to limit the number of results.

Unfortunately, it turns out that the "maxscanrows" and "maxresults"
limits are actually applied *before* the "-m maxchanges" parameter
is considered (experimentally).

Fix the block-size handling so that it gets blocks of changes
limited by revision number ($Start..$Start+$N, etc). This limits
the number of results early enough that both sets of tests pass.

If the --changes-block-size option is not in use, then the code
naturally falls back to the original scheme and gets as many changes
as possible.

Unfortunately, it also turns out that "p4 print" can fail on
files with more changes than "maxscanrows". This fix is unable to
workaround this problem, although in the real world this shouldn't
normally happen.

Signed-off-by: Luke Diamand <luke@diamand.org>
---
 git-p4.py               | 48 +++++++++++++++++++++++++++++++++++-------------
 t/t9818-git-p4-block.sh | 12 ++++++------
 2 files changed, 41 insertions(+), 19 deletions(-)

diff --git a/git-p4.py b/git-p4.py
index 26ad4bc..0e29b75 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -744,41 +744,63 @@ def originP4BranchesExist():
 
 def p4ChangesForPaths(depotPaths, changeRange, block_size):
     assert depotPaths
-    assert block_size
 
     # Parse the change range into start and end
     if changeRange is None or changeRange == '':
-        changeStart = '@1'
-        changeEnd = '#head'
+        changeStart = 1
+        changeEnd = None
     else:
         parts = changeRange.split(',')
         assert len(parts) == 2
-        changeStart = parts[0]
-        changeEnd = parts[1]
+        changeStart = int(parts[0][1:])
+        if parts[1] == '#head':
+            changeEnd = None
+        else:
+            changeEnd = int(parts[1])
 
     # Accumulate change numbers in a dictionary to avoid duplicates
     changes = {}
 
+    # We need the most recent change list number if we're operating in
+    # batch mode. For whatever reason, clients with limited MaxResults
+    # can get this for the entire depot, but not for individual bits of
+    # the depot.
+    if block_size:
+        results = p4CmdList(["changes", "-m", "1"])
+        mostRecentCommit = int(results[0]['change'])
+
     for p in depotPaths:
         # Retrieve changes a block at a time, to prevent running
         # into a MaxScanRows error from the server.
         start = changeStart
-        end = changeEnd
         get_another_block = True
         while get_another_block:
             new_changes = []
             cmd = ['changes']
-            cmd += ['-m', str(block_size)]
-            cmd += ["%s...%s,%s" % (p, start, end)]
+
+            if block_size:
+                end = changeStart + block_size    # only fetch a few at a time
+            else:
+                end = changeEnd             # fetch as many as possible
+
+            if end:
+                endStr = str(end)
+            else:
+                endStr = '#head'
+
+            cmd += ["%s...@%d,%s" % (p, changeStart, endStr)]
             for line in p4_read_pipe_lines(cmd):
                 changeNum = int(line.split(" ")[1])
                 new_changes.append(changeNum)
                 changes[changeNum] = True
-            if len(new_changes) == block_size:
-                get_another_block = True
-                end = '@' + str(min(new_changes))
-            else:
+
+            if not block_size:
+                # Not batched, so nothing more to do
                 get_another_block = False
+            elif end >= mostRecentCommit:
+                get_another_block = False
+            else:
+                changeStart = end + 1
 
     changelist = changes.keys()
     changelist.sort()
@@ -1974,7 +1996,7 @@ class P4Sync(Command, P4UserMap):
         self.syncWithOrigin = True
         self.importIntoRemotes = True
         self.maxChanges = ""
-        self.changes_block_size = 500
+        self.changes_block_size = None
         self.keepRepoPath = False
         self.depotPaths = None
         self.p4BranchesInGit = []
diff --git a/t/t9818-git-p4-block.sh b/t/t9818-git-p4-block.sh
index aae1121..3b3ae1f 100755
--- a/t/t9818-git-p4-block.sh
+++ b/t/t9818-git-p4-block.sh
@@ -49,11 +49,11 @@ test_expect_success 'Default user cannot fetch changes' '
 	! p4 changes -m 1 //depot/...
 '
 
-test_expect_failure 'Clone the repo' '
+test_expect_success 'Clone the repo' '
 	git p4 clone --dest="$git" --changes-block-size=7 --verbose //depot/included@all
 '
 
-test_expect_failure 'All files are present' '
+test_expect_success 'All files are present' '
 	echo file.txt >expected &&
 	test_write_lines outer0.txt outer1.txt outer2.txt outer3.txt outer4.txt >>expected &&
 	test_write_lines outer5.txt >>expected &&
@@ -61,18 +61,18 @@ test_expect_failure 'All files are present' '
 	test_cmp expected current
 '
 
-test_expect_failure 'file.txt is correct' '
+test_expect_success 'file.txt is correct' '
 	echo 55 >expected &&
 	test_cmp expected "$git/file.txt"
 '
 
-test_expect_failure 'Correct number of commits' '
+test_expect_success 'Correct number of commits' '
 	(cd "$git" && git log --oneline) >log &&
 	wc -l log &&
 	test_line_count = 43 log
 '
 
-test_expect_failure 'Previous version of file.txt is correct' '
+test_expect_success 'Previous version of file.txt is correct' '
 	(cd "$git" && git checkout HEAD^^) &&
 	echo 53 >expected &&
 	test_cmp expected "$git/file.txt"
@@ -102,7 +102,7 @@ test_expect_success 'Add some more files' '
 
 # This should pick up the 10 new files in "included", but not be confused
 # by the additional files in "excluded"
-test_expect_failure 'Syncing files' '
+test_expect_success 'Syncing files' '
 	(
 		cd "$git" &&
 		git p4 sync --changes-block-size=7 &&
-- 
2.3.4.48.g223ab37