util: extract stub function to get mtime with second accuracy This function is trivial but will need a long comment why it can't use st.st_mtime. See the next patch for details.

scmutil: add a way for a repo's wlock to be inherited by a subprocess This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances. In the future, we'll call this for custom merge drivers.

scmutil: add a way for a subprocess to be run with an inheritable lock This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances. In an upcoming patch, we'll add an API for the wlock to be inherited.

localrepo: add a way to get the current wlock if it's held This will be useful to pass around a reference to the lock to some functions we're going to add to scmutil. We don't want those functions to live in localrepo to avoid bloat.

localrepo: add a way to get the current lock if it's held We'll use this in upcoming patches to return a reference to the wlock if it's held.

test-help: verify that extension keywords appear in help templates fixed by a2291c9c85a1

templatekw: add {changes}, {distance} and {tag} to the {latesttag} keyword

templater: introduce {latesttag()} function to match a pattern (issue4184) This allows the latest class of tag to be found, such as a release candidate or final build, instead of just the absolute latest. It doesn't appear that the existing keyword can be given an optional argument. There is a keyword, function and filter for 'date', so it doesn't seem harmful to introduce a new function with the same name as an existing keyword. Most functions are pretty Mercurial agnostic, but there is {revset()} as precedent. Even though templatekw.getlatesttags() returns a single tuple, one entry of which is a list, it is simplest to present this as a list of tags instead of a single item, with each tag having a distance and change count attribute. It is also closer to how {latesttag} returns a list of tags, and how this function works when not given a '%' operator.

templatekw: introduce showlatesttags() to handle {latesttag} keywords The keywords {changes}, {distance} and {tag} will be available on a future template method that will allow pattern matching against tag names. For consistency, these should be available on the existing {latesttag} keyword as well. I debated whether or not to add {tag} instead of just continuing with the existing {latesttag}. But it seems clearer not to have the same name for two distinct things (a list in the LHS of %, and an individual tag value on the right). The value of latesttags[0] is the date of commit for the cset to which the tag is applied (i.e. not the date the tag was applied), and therefore isn't made visible because it doesn't seem interesting. It appears that this is merely an internal implementation detail for sorting csets in a stable manner when there are different branches.

templatekw: factor out the changessincetag calculation to a private method This will be reused in the next patch.

templatekw: allow getlatesttags() to match a specific tag pattern This will allow the latest class of tag to be found, such as a release candidate or final build, instead of just the absolute latest. It will be exposed in a future patch. It's unfortunate that the original 'latesttags' cache can't be used to determine the proper values, but it isn't fully populated for the entire repo. For example, the {latesttagdistance} keyword on the Mecurial repo builds the cache up back to the revision for 1.4. If the pattern was 're:^0\.\d$', that wouldn't be in the cache. Maybe this can be optimized some other way, but for now, this is the simpliest implementation.

util: extract stringmatcher() from revset This is used to match against tags, bookmarks, etc in revsets. It will be used in a future patch to do the same tag matching in templater.

util.chunkbuffer: avoid extra mutations when reading partial chunks Previously, a read(N) where N was less than the length of the first available chunk would mutate the deque instance twice and allocate a new str from the slice of the existing chunk. Profiling drawed my attention to these as a potential hot spot during changegroup reading. This patch makes the code more complicated in order to avoid the aforementioned 3 operations. On a pre-generated mozilla-central gzip bundle, this series has the following impact on `hg unbundle` performance on my MacBook Pro: before: 358.21 real 317.69 user 38.49 sys after: 301.57 real 262.69 user 37.11 sys delta: -56.64 real -55.00 user -1.38 sys

util.chunkbuffer: refactor chunk handling logic This will make the next patch easier to read. It provides no benefit on its own.

util.chunkbuffer: special case reading everything The new code results in simpler logic within the while loop. It is also faster since we avoid performing operations on the queue and buf collections. However, there shouldn't be any super hot loops for this since the whole point of chunkbuffer is to avoid reading large amounts of data at once. This does, however, make it easier to optimize chunkbuffer in a subsequent patch.

revert: add reference to backout

backout: add reference to revert

localrepo: allow wlock to be inherited This is part of a series that will allow locks to be inherited by subprocesses in limited circumstances. When allowed, the parent process will pass down requisite information to the child process by way of this environment variable.

lock.release: don't call postrelease functions for inherited locks Review feedback from Pierre-Yves David. The postrelease functions typically assume the lock is not held at all.

lock: turn prepinherit/reacquire into a single context manager Review feedback from Pierre-Yves David. This makes the overall code cleaner and less error-prone, and makes a previously explicitly checked error state impossible.

localrepo: add a note about parentenvvar Review feedback from Pierre-Yves David.

exchange: add "streaming all changes" to bundle2 pulling This is the beginning of client-side support for performing a stream clone using bundle2. The main bundle2 pull function checks whether to perform a streaming clone and outputs a message if so. While we have a duplicate message, it seems easier to have all the bundle2 console writing in one location and in an easy-to-read conditional block.

streamclone: move "streaming all changes" message location Previously, the message was printed after we requested and started processing the remote stream. This seems like something that we should do before calling out to the remote. Moving it also makes it easier to deal with the bundle2 implementation.

streamclone: move payload header generation into own function The stream clone data over the wire protocol contains a header line indicating total file count and data size. In bundle2, this metadata can be captured by a part parameter and doesn't need to be in the body. In preparation for bundle2, have generatev1() return the raw metadata and move the header generation to its own function.