Merge pull request #821 from getappmap/jansorg/indexing-doc

chore: describe indexing of AppMap data

development.md

@@ -0,0 +1,18 @@
+## Indexing of AppMap Data
+
+### Indexed `appmap.yml` Files
+
+`appmap.yml` files, which are located in a project, are indexed.
+The `.appmap.json` files located in the referenced `appmap_dir` directories are indexed automatically,
+as long as these folders are not excluded.
+
+### Excluded `appmap.yml` Files
+
+In the IDE, excluded folders prevent indexing of any data.
+Therefore, we implement `AppMapIndexedRootsSetContributor` to prevent this.
+This class searches for `appmap.yml` files in the content roots of a project.
+Values `appmap_dir` of these files are marked to be indexed even when such directory is excluded.
+
+Content roots are usually the top-level directories of a project.
+Therefore, `appmap.yml` files located in a nested, excluded folder won't be found by this implementation.
+We're not collecting such files because iterating the complete directory tree is expensive without an index.