view relnotes/5.6 @ 49568:da48f170d203

rust-status: query fs traversal metadata lazily

Currently, any time the status algorithm needs to read a directory from the
filesystem (because the stat-only optimization is not available), it also
stats each directory entry eagerly.

Stat'ing the entries is only needed in a few cases (like when checking
the mtime of a directory for caching): this patch creates a wrapper struct
`DirEntry` that only stats the directory entry it represents when needed.

Excerpt of an `strace` before this change on Mozilla Central:

```
openat(AT_FDCWD, ".", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
newfstatat(3, "", {st_mode=S_IFDIR|0755, st_size=3540, ...}, AT_EMPTY_PATH) = 0
getdents64(3, 0x55dc970bd440 /* 139 entries */, 32768) = 5072
statx(3, ".hg", AT_STATX_SYNC_AS_STAT|AT_SYMLINK_NOFOLLOW, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFDIR|0755, stx_size=772, ...}) = 0

[... 135 other successful `statx` calls]

getdents64(3, 0x55dc970bd440 /* 0 entries */, 32768) = 0
close(3)                                = 0
```

After this change:

```
openat(AT_FDCWD, ".", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
newfstatat(3, "", {st_mode=S_IFDIR|0755, st_size=3540, ...}, AT_EMPTY_PATH) = 0
getdents64(3, 0x561567c10190 /* 139 entries */, 32768) = 5072
getdents64(3, 0x561567c10190 /* 0 entries */, 32768) = 0
close(3)                                = 0
```

== New Features ==

 * `hg mv -A` can now be used with `--at-rev`. It behaves just like
   `hg cp -A --at-rev`, i.e. it marks the destination as a copy of the
   source whether or not the source still exists (but the source must
   exist in the parent revision).

 * New revset predicate `diffcontains(pattern)` for filtering revisions
   in the same way as `hg grep --diff pattern`.

 * The memory footprint per changeset and per file during pull/unbundle
   operations has been significantly reduced.


== New Experimental Features ==



== Bug Fixes ==



== Backwards Compatibility Changes ==



== Internal API Changes ==

 * `merge.update()` is now private (renamed to `_update()`). Hopefully
   the higher-level functions available in the same module cover your
   use cases.

 * `phases.registernew` now takes a set of revisions instead of a list
   of nodes. `phases.advanceboundary` takes an optional set of revisions
   in addition to the list of nodes. The corresponeding members of the
   `phasecache` class follow this change.

 * The `addgroup` member of `revlog` classes no longer keeps a list of
   all found nodes. It now returns True iff a node was found in the group.
   An optional callback for duplicated nodes can be used by callers to keep
   track of all nodes themselve.

 * The `_chaininfocache` of `revlog` classes has been changed from a dict
   to a LRU cache.