Support loading custom syntax themes from a file

[acuteenvy]

This Pull Request fixes/closes #2523 & closes #2308.

Custom syntax highlighting themes can be loaded from a .tmTheme file.

If syntax in theme.ron (added in #2532) is a filename that exists in the gitui config directory, it's used as the syntax theme. If not, gitui falls back to selecting from the default theme set.

---

For example, if you put the following in theme.ron:

(
    syntax: Some("mytheme"),
)

gitui will load ~/.config/gitui/mytheme.tmTheme.

---

I followed the checklist:

• I added unittests
• I ran make check without errors
  make check reports a duplicate dependency error:

  error[duplicate]: found 2 duplicate entries for crate 'base64'
  

• I tested the overall application
• I added an appropriate item to the changelog

[acuteenvy]

All tests are running fine for me, I'm not sure why the CI is failing.

[naseschwarz]

All tests are running fine for me, I'm not sure why the CI is failing.

I don't have a solution, but if you want to reproduce, just make sure your gitui config directory does not exist when you run the tests.

If you're on Linux, run XDG_CONFIG_HOME="$(pwd)/foo" cargo test , for example.

[naseschwarz]

I'd wager you've already found it yourself, but just in case you haven't: You removed fs::create_dir_all(&path)?; from get_app_config_path(), which is used in the tests, and moved it to process_cmdline(), which is not used in the tests. The tests try to create a file in the config directory after calling get_app_config_path(), which previously also created the path, but does not anymore.

[acuteenvy]

Thank you, that was it.

[naseschwarz]

The linter failure regarding duplicate deps probably also does not require an exception, as this should be history once we upgrade to ron 0.9.

[extrawurst]

@naseschwarz If thats the last thing here, then lets add a cargo-deny exception in the meantime, merge this, create a followup linking to the upstream issue to remember to clean this up once Ron 0.9 is out?

[acuteenvy]

I found a better way of doing this - it's possible to load themes from the config directory into the default ThemeSet. The user can then put just the theme name in theme.ron, without the .tmTheme extension.

[extrawurst]

nice ron 0.9 just landed aswell

[naseschwarz]

@extrawurst: I have not actually reviewed this, as I was not under the impression that this is ready for review. My remarks were purely in answer to the question about CI failure.

[naseschwarz]

I've looked at this in detail now and find this all quite nicely done.

I've tested this, including error cases I could identify, and found everything working as I would have expected.

We only need to consolidate this with #2570, but I suggest to do this separately.

[extrawurst]

Awesome! Thank you