tags-cache: directly perform a monimal walk for hgtagsfnodescache warming
We do something narrower than the path retrieving data. So lets use dedicated
code instead.
This provides further useful speedup:
### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog
# benchmark.name = hg.debug.debug-update-cache
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.pre-state = warm
before-this-series: 19.947581
skip-fnode-filter: 18.916804 (-5.17%, -1.03)
use-rev-num: 17.493725 (-12.30%, -2.45)
this-changesets: 15.919466 (-20.19%, -4.03)
#require no-windows
$ . "$TESTDIR/remotefilelog-library.sh"
$ hg init master
$ cd master
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> server=True
> serverexpiration=-1
> EOF
$ echo x > x
$ hg commit -qAm x
$ echo y > y
$ hg commit -qAm y
$ echo z > z
$ hg commit -qAm z
$ cd ..
$ hgcloneshallow ssh://user@dummy/master shallow -q
3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
# Compute keepset for 0th and 2nd commit, which implies that we do not process
# the 1st commit, therefore we diff 2nd manifest with the 0th manifest and
# populate the keepkeys from the diff
$ cd shallow
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> pullprefetch=0+2
> EOF
$ hg debugkeepset
# Compute keepset for all commits, which implies that we only process deltas of
# manifests of commits 1 and 2 and therefore populate the keepkeys from deltas
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> pullprefetch=all()
> EOF
$ hg debugkeepset