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
Test attempting a narrow clone against a server that doesn't support narrowhg.
$ . "$TESTDIR/narrow-library.sh"
$ hg init master
$ cd master
$ for x in `$TESTDIR/seq.py 10`; do
> echo $x > "f$x"
> hg add "f$x"
> hg commit -m "Add $x"
> done
$ hg serve -a localhost -p $HGPORT1 --config extensions.narrow=! -d \
> --pid-file=hg.pid
$ cat hg.pid >> "$DAEMON_PIDS"
$ hg serve -a localhost -p $HGPORT2 -d --pid-file=hg.pid
$ cat hg.pid >> "$DAEMON_PIDS"
Verify that narrow is advertised in the bundle2 capabilities:
$ cat >> unquote.py <<EOF
> from __future__ import print_function
> import sys
> if sys.version[0] == '3':
> import urllib.parse as up
> unquote = up.unquote_plus
> else:
> import urllib
> unquote = urllib.unquote_plus
> print(unquote(list(sys.stdin)[1]))
> EOF
$ echo hello | hg -R . serve --stdio | \
> $PYTHON unquote.py | grep narrow
narrow=v0
$ cd ..
$ hg clone --narrow --include f1 http://localhost:$HGPORT1/ narrowclone
requesting all changes
abort: server doesn't support narrow clones
[255]
Make a narrow clone (via HGPORT2), then try to narrow and widen
into it (from HGPORT1) to prove that narrowing is fine and widening fails
gracefully:
$ hg clone -r 0 --narrow --include f1 http://localhost:$HGPORT2/ narrowclone
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets * (glob)
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd narrowclone
$ hg tracked --addexclude f2 http://localhost:$HGPORT1/
comparing with http://localhost:$HGPORT1/
searching for changes
looking for local changes to affected paths
$ hg tracked --addinclude f1 http://localhost:$HGPORT1/
comparing with http://localhost:$HGPORT1/
searching for changes
no changes found
abort: server doesn't support narrow clones
[255]