nodemap: introduce append-only incremental update of the persistent data
Rewriting the full nodemap for each transaction has a cost we would like to
avoid. We introduce a new way to write persistent nodemap data by adding new
information at the end for file. Any new and updated block as added at the end
of the file. The last block is the new root node.
With this method, some of the block already on disk get "dereferenced" and
become dead data. In later changesets, We'll start tracking the amount of dead
data to eventually re-generate a full nodemap.
Differential Revision: https://phab.mercurial-scm.org/D7886
#require execbit
Create extension that can disable exec checks:
$ cat > noexec.py <<EOF
> from mercurial import extensions, util
> def setflags(orig, f, l, x):
> pass
> def checkexec(orig, path):
> return False
> def extsetup(ui):
> extensions.wrapfunction(util, 'setflags', setflags)
> extensions.wrapfunction(util, 'checkexec', checkexec)
> EOF
$ hg init unix-repo
$ cd unix-repo
$ touch a
$ hg add a
$ hg commit -m 'unix: add a'
$ hg clone . ../win-repo
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ chmod +x a
$ hg commit -m 'unix: chmod a'
$ hg manifest -v
755 * a
$ cd ../win-repo
$ touch b
$ hg add b
$ hg commit -m 'win: add b'
$ hg manifest -v
644 a
644 b
$ hg pull
pulling from $TESTTMP/unix-repo
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)
new changesets 2d8bcf2dda39
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg manifest -v -r tip
755 * a
Simulate a Windows merge:
$ hg --config extensions.n=$TESTTMP/noexec.py merge --debug
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: a03b0deabf2b, local: d6fa54f68ae1+, remote: 2d8bcf2dda39
a: update permissions -> e
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
Simulate a Windows commit:
$ hg --config extensions.n=$TESTTMP/noexec.py commit -m 'win: merge'
$ hg manifest -v
755 * a
644 b
$ cd ..