extdata: add extdatasource reader
This adds basic support for extdata, a way to add external data
sources for revsets and templates. An extdata data source is simply a
list of lines of the form:
<revision identifier>[<space><freeform text>]\n
An extdata source is configured thusly:
[extdata]
name = <a url or path>
urls of the form shell: are launch shell commands to generate data.
This patch is slightly modified by Yuya Nishihara as follows:
- fix typo
- remove unused function
- remove future expansion point for parameter (which can be added later
as the extdata revset/template are experimental)
You can see the original patch at
https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-September/088426.html
syntax: glob
*.elc
*.tmp
*.orig
*.rej
*~
*.mergebackup
*.o
*.so
*.dll
*.exe
*.pyd
*.pyc
*.pyo
*$py.class
*.swp
*.prof
*.zip
\#*\#
.\#*
tests/.coverage*
tests/.testtimes*
tests/.hypothesis
tests/hypothesis-generated
tests/annotated
tests/*.err
tests/htmlcov
build
contrib/chg/chg
contrib/hgsh/hgsh
contrib/vagrant/.vagrant
contrib/docker/debian-*
contrib/docker/ubuntu-*
dist
packages
doc/common.txt
doc/*.[0-9]
doc/*.[0-9].txt
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
MANIFEST.in
patches
mercurial/__modulepolicy__.py
mercurial/__version__.py
mercurial/hgpythonlib.h
mercurial.egg-info
.DS_Store
tags
cscope.*
.idea/*
.asv/*
i18n/hg.pot
locale/*/LC_MESSAGES/hg.mo
hgext/__index__.py
# Generated wheels
wheelhouse/
syntax: regexp
^\.pc/
^\.(pydev)?project
# hackable windows distribution additions
^hg-python
^hg.py$