-S reports the check-ins where the occurrence count of PATTERN changed, -G those where a changed line mentions it. A string added once and deleted later is two lines, where plain grep reports every version that held it in between.

The issue expected this to need a diff per revision. It does not: a path whose blob hash matches its parent's cannot have moved either answer, so the walk compares F-card hashes and reads only the blobs that changed. Deletions are picked up from the parent side, which a walk over the child's files alone would miss.

Merges compare against the primary parent, as git log -S does; counting against every parent reports one appearance twice. check-in: 28c48bb3f7 user: dmestas tags: trunk