fsmonitor: acquire localrepo.wlock prior to emitting hg.update state
we see some weird things in the watchman logs where the mercurial
process is seemingly confused about which hg.update state it is publishing
through watchman.
On closer examination, we're seeing conflicting pids for the clients involved
and this implies a race.
To resolve this, we extend the wlock around the state-enter/state-leave
events that are emitted to watchman.
Test Plan:
Some manual testing:
In one window, run this, and then checkout a different rev:
```
$ watchman -p -j <<<'["subscribe", "/data/users/wez/fbsource", "wez", {"expression": ["name", ".hg/updatestate"]}]'
{
"version": "4.9.0",
"subscribe": "wez",
"clock": "c:1495034090:814028:1:312576"
}
{
"state-enter": "hg.update",
"version": "4.9.0",
"clock": "c:1495034090:814028:1:312596",
"unilateral": true,
"subscription": "wez",
"metadata": {
"status": "ok",
"distance": 125,
"rev": "a1275d79ffa6c58b53116c8ec401c275ca6c1e2a",
"partial": false
},
"root": "/data/users/wez/fbsource"
}
{
"root": "/data/users/wez/fbsource",
"metadata": {
"status": "ok",
"distance": 125,
"rev": "a1275d79ffa6c58b53116c8ec401c275ca6c1e2a",
"partial": false
},
"subscription": "wez",
"unilateral": true,
"version": "4.9.0",
"clock": "c:1495034090:814028:1:312627",
"state-leave": "hg.update"
}
```
Tailed the watchman log file and looked for invalid state assertion errors,
then ran my `rebase-all` script to update/rebase all of my heads.
Didn't trigger the error condition (but couldn't reliably trigger it previously
anyway), and the output captured above shows that the states are being emitted
correctly.
# Extract version number into 4 parts, some of which may be empty:
#
# version: the numeric part of the most recent tag. Will always look like 1.3.
#
# type: if an rc build, "rc", otherwise empty
#
# distance: the distance from the nearest tag, or empty if built from a tag
#
# node: the node|short hg was built from, or empty if built from a tag
gethgversion() {
make cleanbutpackages
make local || make local PURE=--pure
HG="$PWD/hg"
$HG version > /dev/null || { echo 'abort: hg version failed!'; exit 1 ; }
hgversion=`$HG version | sed -ne 's/.*(version \(.*\))$/\1/p'`
if echo $hgversion | grep + > /dev/null 2>&1 ; then
tmp=`echo $hgversion | cut -d+ -f 2`
hgversion=`echo $hgversion | cut -d+ -f 1`
distance=`echo $tmp | cut -d- -f 1`
node=`echo $tmp | cut -d- -f 2`
else
distance=''
node=''
fi
if echo $hgversion | grep -- '-' > /dev/null 2>&1; then
version=`echo $hgversion | cut -d- -f1`
type=`echo $hgversion | cut -d- -f2`
else
version=$hgversion
type=''
fi
}