gplugin/gplugin

Create gobject-introspection to make native plugins introspectable

11 months ago, Gary Kramlich
fd779d79a546
Create gobject-introspection to make native plugins introspectable

There's a lot to this, but the documentation covers the consumer side. From
the GPlugin developer side, we basically created static library that manually
loads plugins and is setup in a way to be called via g-ir-scanner's --program
argument.

Testing Done:
Ran the new unit tests that test gir generation. Also installed to a local prefix and used that to compile a binary against `gplugin-introspection` and verified it displayed the proper output for `--help`.

Reviewed at https://reviews.imfreedom.org/r/2458/
## clang-format
GPlugin uses [clang-format][1] to automatically format code. Version 9 (or
higher) is required. Earlier versions will fail on the options in the
`.clang-format` file.
You can use clang-format in one or more of the following ways:
* Integrate it into your editor. The [clang-format page][1] has examples.
* Use a Mercurial [hook script][2].
* Run `ninja clang-format` from your build directory.
* Worst case, run `clang-format -i SOME_FILE` manually.
### GObject Functions
GObject and GPlugin have functions which take pairs of name/value arguments:
* `g_object_get()`
* `g_object_new()`
* `gplugin_plugin_info_new()`
If code calling one of these functions with such pairs has to be wrapped, the
pairs are easier to read and edit with manual formatting to group the name and
value on the same line (but otherwise following the usual formatting that
clang-format would apply):
```
/* clang-format off */
g_object_get(
G_OBJECT(info),
"name", &name,
"summary", &summary,
NULL);
/* clang-format on */
```
### Debian
Debian and derivatives (e.g. Ubuntu) ship clang-format version 9 in a package
named `clang-format-9`. The package named `clang-format` is currently an
older version. Additionally, the `clang-format-9` package will not place a
`clang-format` in the `$PATH`. Install as follows:
```
sudo apt install clang-format-9
sudo update-alternatives --set clang-format /usr/bin/clang-format-9
```
## convey
GPlugin uses [Convey][3] for CI. You can run the integration tests locally.
To initially setup Convey, which requires Docker:
1. Install Convey. You can use a pre-built binary from [convey's Downloads
page][4]; put that (or a symlink) in your `$PATH` named `convey`.
For now, avoid version 0.14.
2. Install Docker. On Debian systems, use: `sudo apt install docker.io`
3. Add yourself to the `docker` group. Adding yourself to a group does not
add that group to your existing session, so the first time you will need to
get a shell in that group with `newgrp docker` or by rebooting.
To run all of the integration tests, run the "all" metaplan:
```
convey all
```
To run a specific test/platform, run the plan directly:
```
convey alpine-edge-amd64
```
To get a list of metaplans and their plans:
```
convey list metaplans
```
[1]: https://clang.llvm.org/docs/ClangFormat.html
[2]: https://hg.mozilla.org/projects/nss/file/default/coreconf/precommit.clang-format.sh
[3]: https://keep.imfreedom.org/grim/convey
[4]: https://bintray.com/pidgin/releases/convey