This CL optimizes CheckForCommitObjects in two ways:
- Fast Path: If the raw `git ls-tree` output does not contain `160000` (gitlink mode), return early. This avoids parsing entirely for repositories without submodules at the cost of about 3ms.
- Iterative Parsing: For repositories with submodules, use an iterative find loop to locate gitlink entries instead of splitting the entire tree content.
On the Chromium repo:
- Speed: The parsing step is ~7.7x faster (0.04s vs 0.30s).
- Memory: Saves ~78 MB of memory per run by avoiding the creation of ~300,000 string objects during the split.
I also added tests now that it's more than a simple loop.
Change-Id: I903effc50aaedb9130772491ad38385b22477d58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/7231149
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Josiah Kiehl <kiehl@google.com>
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