`click-man` versions < 0.3.0 do not properly support multiple
entrypoints. Since this was added to `tox` after `0.3.0` was released,
`tox` should never be pulling older versions. But, let's add it here for
documentation purposes.

See
!1107 (comment 135187046)
for some background on this.

tox.ini: Specify minimum version of click-man

See merge request !1120

Chandan Singh authored Jan 29, 2019 and Chandan Singh committed Jan 31, 2019

We use output of `git --version` to determine if we can run some tests
that rely on features from newer git versions. Usually, we expect the
output to be like:

    git version 2.17.2

On some platforms, like MacOS, there could be a suffix after the version
string, so that it looks something like:

    git version 2.17.2 (Apple Git-113)

This causes things to fail like so:

    ValueError: invalid literal for int() with base 10: '2 (Apple Git-113)\n'

Fix logic around `HAVE_OLD_GIT` such that we split the output of
`git --version` without limit on how many times we split. Previously we
used to split only twice so the suffixes like `(Apple Git-113)` are not
part of the parsed version.

testutils/site.py: Support parsing more exotic git versions

See merge request !1118

This removes the need for the 'Dependency' list to then be matched
with the corresponding LoadElement and will allow iterating the
graph more easily

This simplifies the loading

Cleanup loader by linking LoadElements sooner

See merge request !1122

tests/cachekey: Test cache keys are independent of target elements

See merge request !1123

Improve our filter documentation

Closes #278

See merge request !1112

This patch also uncovered the fact that our test_filter_deps_ok() test
has been inaccurate. Thus the element built in this test
(deps-permitted.bst) has been modified so that it build depends on the
input.bst element, as it should.

tests/filter.py: Ensure deps_ok test passes