docs: add documentation for the baseline feature

src/config.rs

@@ -103,7 +103,7 @@ pub struct GooseConfiguration {
     /// Create reports, can be used multiple times (supports .html, .htm, .md, .json)
     #[options(no_short, meta = "NAME")]
     pub report_file: Vec<String>,
-    /// An optional baseline, for rendering the report
+    /// An optional baseline JSON report, for rendering the reports with deltas
     #[options(no_short, meta = "NAME")]
     pub baseline_file: Option<String>,
     /// Disable granular graphs in report file
@@ -286,7 +286,7 @@ pub(crate) struct GooseDefaults {
     pub no_error_summary: Option<bool>,
     /// An optional default for the html-formatted report file name.
     pub report_file: Option<Vec<String>>,
-    /// An optional baseline file for the reports.
+    /// /// An optional baseline JSON report, for rendering the reports with deltas
     pub baseline_file: Option<String>,
     /// An optional default for the flag that disables granular data in HTML report graphs.
     pub no_granular_report: Option<bool>,

src/docs/goose-book/src/getting-started/metrics.md

@@ -352,3 +352,15 @@ The JSON report is a dump of the internal metrics collection. It is a JSON seria
 
 ### Developer documentation
 Additional details about how metrics are collected, stored, and displayed can be found [in the developer documentation](https://docs.rs/goose/*/goose/metrics/index.html).
+
+## Baseline deltas
+
+It is possible to use a previously generated JSON report as a baseline for reports. In addition to the actual values, this will then also show the difference from the last.
+
+To use this, you will need to:
+
+* Create a baseline report by running it at least once using `--report-file report.json`
+* Then start adding `--baseline-file report.json` to later runs
+
+It is possible to still keep generating a JSON report at the same time as using a baseline file. So that you can
+create the next basefile in the same step.

src/docs/goose-book/src/getting-started/runtime-options.md

@@ -34,6 +34,7 @@ Metrics:
   --no-print-metrics          Doesn't display metrics at end of load test
   --no-error-summary          Doesn't display an error summary
   --report-file NAME          Create reports, can be used multiple times (supports .html, .htm, .md, .json)
+  --baseline-file NAME        An optional baseline JSON report, for rendering the reports with deltas
   --no-granular-report        Disable granular graphs in report file
   -R, --request-log NAME      Sets request log file name
   --request-format FORMAT     Sets request log format (csv, json, raw, pretty)