theme presets added

[Cetttok]

created new module (themepresetmanager) and integrate it to conky in main.c. implemented:

• user can specify theme preset by alias in conifg option eg conky -c lean
• theme presets stored in git repo with simple struct (themealias.theme - folder name and everywords.conf - main config name)
• operations with git realise with libgit2 and I dont now there correct add includes ( in CMakeLists.txt files)
• i dont know where i must to store my h and cpp files
• this code testes with /var/lib/conky/themes repo path and exapmle repo https://github.com/Cetttok/testRepoForConkyThemes
• this code cant clone repo with submodules and i dont know is it necessary please view and say me what i must correct i ready to perform yours requirements

Related to #2142

sorry for my English

[netlify[bot]]

✅ Deploy Preview for conkyweb canceled.

Name	Link
🔨 Latest commit	bb133b86c150509ca9557dc06a51e892d8a4cee2
🔍 Latest deploy log	https://app.netlify.com/projects/conkyweb/deploys/69230d3ade941500083e1ac8

[Cetttok]

maybe need to add gitlib2 to dependencies and i didn know how to do it :(

[Cetttok]

guys build test done! Maybe somebody say me that i do uncorrect?

[Cetttok]

to be honest, I don't understand why nix crashes.

[Cetttok]

Halo guys! I make most of all that @Caellian told me. That changed in last commits:

• repo not pulling of every path replacing request. only pulling one folder or subrepo of requested theme
• fixed memory leaks for libgit2
• build options (bool BUILD_PRESETS string PRESETS_REPO_URL PRESETS_REPO_PATH)
• code used libgit masked in it option
• repo configuration file in xml (repo.conf) example in theme-presets-manager.h after advanced_repo_source declaration
• code in conky code style
• clang format on my module
• add loging about long operations (eg pulling ont theme) and theme presets repo that used
• adding support custom branches in non main repo (in submodules etc)
• git fetch git clone and another standart (and not standart) methods realised thats not all.

[Cetttok]

@Caellian i know that it is opensource (free of all) but will be nice (for me) if you maybe say my Judgment for this