stream-clone: disable gc for the initial section for the v3 format
The number of small container created turn Python in a gc-frenzy that seriously
impact performance.
This significantly boost performance. The following number comes from a large
private repository using perf::stream-locked-section:
base-line: 35.04 seconds
prev-change: 24.51 seconds (-30%)
prev-change: 20.88 seconds (-40%)
this-change: 14.22 seconds (-60% from baseline; -31% from prev)
$ cat >> $HGRCPATH <<EOF
> [censor]
> policy=ignore
> EOF
$ mkdir r
$ cd r
$ hg init
$ echo secret > target
$ hg commit -Am "secret"
adding target
$ touch bystander
$ hg commit -Am "innocent"
adding bystander
$ echo erased-secret > target
$ hg commit -m "erased secret"
$ hg censor target --config extensions.censor= -r ".^^"
checking for the censored content in 1 heads
checking for the censored content in the working directory
censoring 1 file revisions
$ hg update ".^"
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat target
$ hg update tip
1 files updated, 0 files merged, 0 files removed, 0 files unresolved