v2.8.0

Added

• Server-side concurrency lock to serialize concurrent
  deployments (closes the risk from PROPOSAL.md §5 #6: "two
  simultaneous workflows to the same FTP can corrupt each
  other"). The default is OFF to preserve the v2.7.0
  behaviour bit-for-bit. Opt in with the new input
  concurrency_lock: "true".

  - uses: airvzxf/ftp-deployment-action@v2
    with:
      server: ${{ secrets.FTP_SERVER }}
      user: ${{ secrets.FTP_USERNAME }}
      password: ${{ secrets.FTP_PASSWORD }}
      concurrency_lock: "true"

  Mechanism. Before the mirror, lftp issues quote MKD <path> to create a sentinel directory on the FTP server.
  RFC 959 MKD and RMD are implemented by every FTP
  server (vsftpd, proftpd, Pure-FTPd, sftp-via-FTP-gateways,
  etc.) and mkdir(2) is atomic on virtually every UNIX-like
  filesystem (returning EEXIST if the directory already
  exists). The race window between two clients is
  microseconds, and the worst-case outcome — the lock
  briefly staying held by a dead runner — is caught by the
  configurable concurrency_lock_timeout. We chose
  MKD/RMD because lftp has no built-in server-side
  lock command (it only has file:use-lock for local
  files, which we verified against the lftp 4.9.3 source
  and the src/commands.cc static command table).

  Inputs.

  • concurrency_lock (default false) — opt-in switch.
  • concurrency_lock_path (default .lftp-deployment.lock)
    — sentinel directory; validated with the same
    validate_path rules as local_dir / remote_dir
    (rejects .., leading dash, control chars, and shell
    metacharacters).
  • concurrency_lock_timeout (default 300) — maximum
    seconds to wait for the lock when another run is
    currently holding it. 0 means "fail immediately when
    held" (no polling).
  • concurrency_lock_poll_interval (default 5) — seconds
    between quote MKD attempts. Rejected when 0 (would
    cause a division-by-zero in the iteration count).

  Release. The lock is released in three layered ways:
  (1) an inline quote RMD <path> in the lftp -e script
  right before quit;; (2) a fallback run_lftp_lock_release
  call in the EXIT trap (so a signal-killed lftp still
  releases the lock, using the .netrc that is also about to
  be removed); (3) the documentation in the README explains
  the manual quote RMD recovery path for the rare case of
  a stale lock (holder died before any of the above could
  run). When concurrency_lock is false (the default),
  run_lftp_lock_release short-circuits on an empty lock
  path and never invokes lftp, so the no-op path is bit-for-
  bit identical to v2.7.0.

  When to use it. For the common case of a single
  workflow deploying to one FTP, the GitHub Actions
  concurrency: block is the recommended approach
  (documented as Option A in the new README section "Concurrency /
  deployment lock") because it works across runners and
  regions, requires no extra inputs, and is platform-managed.
  The concurrency_lock input is the fallback for users who
  cannot add a concurrency: block (e.g. multiple distinct
  workflows pointing to the same FTP, or deploys driven by a
  tool the user does not own).

Internal

• lib.sh: new functions build_lock_acquire_script,
  build_lock_release_script, and run_lftp_lock_release.
  All three read the new inputs via _indirection (the
  project's single point of dynamic variable-name lookup);
  no second eval site is introduced.
• lib.sh: run_lftp_once now takes two extra parameters
  (lock acquire / release fragments). When the lock is
  disabled, both are empty strings, so the composed
  lftp -e script is bit-for-bit identical to v2.7.0.
• lib.sh: print_inputs_dump now lists the four new
  inputs in both debug and non-debug modes.
• entrypoint.sh: the new inputs are defaulted to their
  action.yml defaults; validate_path /
  validate_int are run only when the lock is enabled,
  to keep the validation surface tight for the common
  case (concurrency_lock=false). The EXIT trap is
  extended to call run_lftp_lock_release before
  removing the .netrc (so lftp can still authenticate
  the release call).
• Tests: 11 new bats unit tests in tests/unit/lock.bats
  cover the empty/non-empty branches, the timeout=0
  short-circuit, the ceil(timeout/poll) iteration count
  for both 300/5 and 300/7, the lock path verbatim pass-
  through, and the no-op paths of run_lftp_lock_release.
  3 new smoke tests in tests/smoke.sh verify the
  default-off path emits no lock fragments in the lftp
  script, and that .. in concurrency_lock_path and
  0 in concurrency_lock_poll_interval are both
  rejected with exit 2.
• tests/contract.sh was unchanged: it auto-discovers the
  four new inputs from the new lib.sh::print_inputs_dump
  list and from the static INPUT_* references in
  entrypoint.sh / lib.sh, and matches them against
  action.yml (now 31 declared inputs).
• Total test count: 118 unit + 33 smoke + 1 contract + 3
  release-smoke = 155 tests, all green.