mirror of
https://github.com/git/git.git
synced 2026-01-11 21:33:13 +09:00
2d46e361fd
When a lock file is held, it can be helpful to know which process owns it, especially when debugging stale locks left behind by crashed processes. Add an optional feature that creates a companion PID file alongside each lock file, containing the PID of the lock holder. For a lock file "foo.lock", the PID file is named "foo~pid.lock". The tilde character is forbidden in refnames and allowed in Windows filenames, which guarantees no collision with the refs namespace (e.g., refs "foo" and "foo~pid" cannot both exist). The file contains a single line in the format "pid <value>" followed by a newline. The PID file is created when a lock is acquired (if enabled), and automatically cleaned up when the lock is released (via commit or rollback). The file is registered as a tempfile so it gets cleaned up by signal and atexit handlers if the process terminates abnormally. When a lock conflict occurs, the code checks for an existing PID file and, if found, uses kill(pid, 0) to determine if the process is still running. This allows providing context-aware error messages: Lock is held by process 12345. Wait for it to finish, or remove the lock file to continue. Or for a stale lock: Lock was held by process 12345, which is no longer running. Remove the stale lock file to continue. The feature is controlled via core.lockfilePid configuration (boolean). Defaults to false. When enabled, PID files are created for all lock operations. Existing PID files are always read when displaying lock errors, regardless of the core.lockfilePid setting. This ensures helpful diagnostics even when the feature was previously enabled and later disabled. Signed-off-by: Paulo Casaretto <pcasaretto@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>