chore(docs): Explicitly mention that llvm-version must be the major version

Author: whisperity

README.md

@@ -300,12 +300,12 @@ Please refer to earlier parts of the documentation for the configuration of thes
 
 ### Versions to install
 
-| Variable         | Default                                                          | Description                                                                                                                                                                                                                                                               |
-|------------------|------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| `llvm-version`   | `latest`                                                         | The major version of LLVM to install and use. LLVM is installed from [PPA](http://apt.llvm.org/). If `latest`, automatically gather the latest version. If `ignore`, don't install anything. (Not recommended)                                                            |
-| `install-custom` | `false`                                                          | If set to `true`, opens the ability to locally clone and install CodeChecker from the specified `repository` and `version`. Otherwise, `version` is taken as a release version, and the [CodeChecker suite from PyPI](http://pypi.org/project/codechecker) is downloaded. |
-| `repository`     | [`Ericsson/CodeChecker`](http://github.com/Ericsson/CodeChecker) | The CodeChecker repository to check out and build, if `install-custom` is `true`.                                                                                                                                                                                         |
-| `version`        | `master`                                                         | If `install-custom` is `false`, the release version (e.g. `6.18.0`) to download from PyPI, or `master` to fetch the latest release. Otherwise, the branch (defaulting to `master`), tag, or commit SHA in the `repository` to check out.                                  |
+| Variable         | Default                                                          | Description                                                                                                                                                                                                                                                                                                                                      |
+|------------------|------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `llvm-version`   | `latest`                                                         | The major version of LLVM to install and use. LLVM is installed from the community [PPA](http://apt.llvm.org/). The value **MUST** be a major version (e.g. `13`) that is supported by the _PPA_ for the OS used! If `latest`, automatically gather the latest (yet unreleased) version. If `ignore`, don't install anything. (Not recommended.) |
+| `install-custom` | `false`                                                          | If set to `true`, opens the ability to locally clone and install CodeChecker from the specified `repository` and `version`. Otherwise, `version` is taken as a release version, and the [CodeChecker suite from PyPI](http://pypi.org/project/codechecker) is downloaded.                                                                        |
+| `repository`     | [`Ericsson/CodeChecker`](http://github.com/Ericsson/CodeChecker) | The CodeChecker repository to check out and build, if `install-custom` is `true`.                                                                                                                                                                                                                                                                |
+| `version`        | `master`                                                         | If `install-custom` is `false`, the release version (e.g. `6.18.0`) to download from PyPI, or `master` to fetch the latest release. Otherwise, the branch (defaulting to `master`), tag, or commit SHA in the `repository` to check out.                                                                                                         |
 
 ### Build log configuration
 

action.yml

@@ -19,7 +19,7 @@ inputs:
     required: true
     default: 'master'
   llvm-version:
-    description: 'The major version of LLVM to install and use. LLVM is installed from PPA. If "latest", automatically gather the latest version. If "ignore", do not install anything. (Not recommended)'
+    description: 'The major version of LLVM to install and use. LLVM is installed from the community PPA at http://apt.llvm.org. The value MUST be a major version (e.g. 13) that is supported by the PPA for the OS used! If "latest", automatically gather the latest version. If "ignore", do not install anything. (Not recommended.)'
     required: true
     default: 'latest'