internals: document CBOR utilization
I spoke with some people at Mozilla about CBOR and they advised me
that we should be careful about the subset of CBOR we use in order
to mitigate security, performance, and compatibility concerns.
This commit establishes a document that attempts to formalize our
use of CBOR.
Its main limitations are on what types are allowed. It explicitly
enumerates which types are supported. Notable missing features
include:
* Indefinite-length arrays and maps
* Text strings (bytes all the way)
* Floats
* Date/time types
* Big integers
* Use of indefinite-length byte strings for map keys, values in
containers.
If we have a need for any of these, we can have a discussion about
them when the time comes.
Differential Revision: https://phab.mercurial-scm.org/D4412
#require unix-permissions no-root no-windows
Prepare
$ hg init a
$ echo a > a/a
$ hg -R a ci -A -m a
adding a
$ hg clone a b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
Test that raising an exception in the release function doesn't cause the lock to choke
$ cat > testlock.py << EOF
> from mercurial import error, registrar
>
> cmdtable = {}
> command = registrar.command(cmdtable)
>
> def acquiretestlock(repo, releaseexc):
> def unlock():
> if releaseexc:
> raise error.Abort(b'expected release exception')
> l = repo._lock(repo.vfs, b'testlock', False, unlock, None, b'test lock')
> return l
>
> @command(b'testlockexc')
> def testlockexc(ui, repo):
> testlock = acquiretestlock(repo, True)
> try:
> testlock.release()
> finally:
> try:
> testlock = acquiretestlock(repo, False)
> except error.LockHeld:
> raise error.Abort(b'lockfile on disk even after releasing!')
> testlock.release()
> EOF
$ cat >> $HGRCPATH << EOF
> [extensions]
> testlock=$TESTTMP/testlock.py
> EOF
$ hg -R b testlockexc
abort: expected release exception
[255]
One process waiting for another
$ cat > hooks.py << EOF
> import time
> def sleepone(**x): time.sleep(1)
> def sleephalf(**x): time.sleep(0.5)
> EOF
$ echo b > b/b
$ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
$ hg -R b up -q --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
> > preup-stdout 2>preup-stderr
$ wait
$ cat preup-stdout
$ cat preup-stderr
waiting for lock on working directory of b held by process '*' on host '*' (glob)
got lock after * seconds (glob)
$ cat stdout
adding b
On processs waiting on another, warning after a long time.
$ echo b > b/c
$ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
$ hg -R b up -q --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
> --config ui.timeout.warn=250 \
> > preup-stdout 2>preup-stderr
$ wait
$ cat preup-stdout
$ cat preup-stderr
$ cat stdout
adding c
On processs waiting on another, warning disabled.
$ echo b > b/d
$ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
$ hg -R b up -q --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
> --config ui.timeout.warn=-1 \
> > preup-stdout 2>preup-stderr
$ wait
$ cat preup-stdout
$ cat preup-stderr
$ cat stdout
adding d
check we still print debug output
On processs waiting on another, warning after a long time (debug output on)
$ echo b > b/e
$ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
$ hg -R b up --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
> --config ui.timeout.warn=250 --debug\
> > preup-stdout 2>preup-stderr
$ wait
$ cat preup-stdout
calling hook pre-update: hghook_pre-update.sleephalf
waiting for lock on working directory of b held by process '*' on host '*' (glob)
got lock after * seconds (glob)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat preup-stderr
$ cat stdout
adding e
On processs waiting on another, warning disabled, (debug output on)
$ echo b > b/f
$ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
$ hg -R b up --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
> --config ui.timeout.warn=-1 --debug\
> > preup-stdout 2>preup-stderr
$ wait
$ cat preup-stdout
calling hook pre-update: hghook_pre-update.sleephalf
waiting for lock on working directory of b held by process '*' on host '*' (glob)
got lock after * seconds (glob)
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cat preup-stderr
$ cat stdout
adding f
Pushing to a local read-only repo that can't be locked
$ chmod 100 a/.hg/store
$ hg -R b push a
pushing to a
searching for changes
abort: could not lock repository a: Permission denied
[255]
$ chmod 700 a/.hg/store