Merge pull request #1425 from ahoppen/more-docs

Add some more overview documentation documents

Author: ahoppen

Documentation/Environment Variables.md

@@ -0,0 +1,19 @@
+# Environment variables
+
+The following environment variables can be used to control some behavior in SourceKit-LSP
+
+## Build time
+
+- `SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER`: Use the `NonDarwinLogger` to log to stderr, even when building SourceKit-LSP on macOS. This is useful when running tests using `swift test` because it writes the log messages to stderr, which is displayed during the `swift test` invocation.
+- `SOURCEKIT_LSP_CI_INSTALL`: Modifies rpaths in a way that’s necessary to build SourceKit-LSP to be included in a distributed toolchain. Should not be used locally.
+- `SWIFTCI_USE_LOCAL_DEPS`: Assume that all of SourceKit-LSP’s dependencies are checked out next to it and use those instead of cloning the repositories. Primarily intended for CI environments that check out related branches.
+
+## Runtime
+
+- `SOURCEKITLSP_LOG_LEVEL`: When using `NonDarwinLogger`, specify the level at which messages should be logged. Defaults to `default`. Use `debug` to increase to the highest log level.
+- `SOURCEKITLSP_LOG_PRIVACY_LEVEL`: When using `NonDarwinLogger`, specifies whether information that might contain personal information (essentially source code) should be logged. Defaults to `private`, which logs this information. Set to `public` to redact this information.
+
+## Testing
+- `SKIP_LONG_TESTS`: Skip tests that typically take more than 1s to execute.
+- `SOURCEKITLSP_KEEP_TEST_SCRATCH_DIR`: Does not delete the temporary files created during test execution. Allows inspection of the test projects after the test finishes.
+- `SOURCEKIT_LSP_TEST_MODULE_CACHE`: Specifies where tests should store their shared module cache. Defaults to writing the module cache to a temporary directory. Intended so that CI systems can clean the module cache directory after running.