bundle2: safely read unpack data from part header We use the same approach that the other unpack, as function is given the struct format and his both responsible for reading the right amount of data from the header and unpack the struct. This give use flexibility if we decide to change the size of something in the format before the release.

transaction: drop extra import caught by pyflakes

fncache: clean up fncache during strips Previously the fncache was cleaned up at read time by noticing when it was out of sync. This caused writes to happen outside the scope of transactions and could have caused race conditions. With this change, we'll keep the fncache up-to-date as we go by removing old entries during repair.strip.

caches: invalidate store caches when lock is taken The fncache was not being properly invalidated each time the lock was taken, so in theory it could contain old data from prior to the caller having the lock. This changes it to be invalidated as soon as the lock is taken (same as all our other caches).

fncache: move fncache writing to be in a transaction Previously the fncache was written at lock.release time. This meant it was not tracked by a transaction, and if an error occurred during the fncache write it would fail to update the fncache, but would not rollback the transaction, resulting in an fncache that was not in sync with the files on disk (which causes verify to fail, and causes streaming clones to not copy all the revlogs). This uses the new transaction backup mechanism to make the fncache transacted. It also moves the fncache from being written at lock.release time, to being written at transaction.close time.

transaction: add support for non-append files This adds support for normal, non-append-only files in transactions. For example, .hg/store/fncache and .hg/store/phaseroots should be written as part of the transaction, but are not append only files. This adds a journal.backupfiles along side the normal journal. This tracks which files have been backed up as part of the transaction. transaction.addbackup() creates a backup of the file (using a hardlink), which is later used to recover in the event of the transaction failing. Using a seperate journal allows the repository to still be used by older versions of Mercurial. A future patch will use this functionality and add tests for it.

transaction: add onclose/onabort hook for pre-close logic Adds an optional onclose parameter to transactions that gets called just before the transaction is committed. This allows things that build up data over the course of the transaction (like the fncache) to commit their data. Also adds onabort. It's not used, but will allow extensions to hook into onclose and onabort to provide transaction support.