Adds a logging section in the contributing guidelines

CONTRIBUTING.md

@@ -11,3 +11,26 @@ Contributors need to [sign our CLA](https://cla-assistant.io/trufflesecurity/tru
 ## Adding new secret detectors
 
 We have published some [documentation and tooling to get started on adding new secret detectors](hack/docs/Adding_Detectors_external.md). Let's improve detection together!
+
+## Logging in TruffleHog
+
+**Use fields over format strings**. For structured logging, fields allow us to better filter and search through logs than embedding data in the message.
+
+**Differentiate logs coming from dependencies**. This can be done with a `"dep"` field that gets passed to the library. Sometimes it’s not possible to do this.
+
+Limit log levels to _**info**_ (indicate normal or expected operation) and _**error**_ (functionality is impeded and should be checked by an engineer)
+
+**Choose an appropriate verbosity level**
+```
+0. — logs we always want to see
+1. — logs we could possibly want to turn off
+2. — logs that are useful for debugging
+3. — frequently called logs that may produce a lot of output
+4. — extremely verbose logs or logs containing sensitive information
+5. — ultimate verbosity
+```
+Example: `Logger().V(2).Info("skipping file: extension is ignored", "ext", mimeExt)`
+
+**Either log an error or return it**. Doing one or the other will help defer logging for when there is more context for it and prevent duplicate “bubbling up” logs.
+
+**Log contextual information**. Every log emitted should contain this context via fields to easily filter and search.