ci/images: add debian-11-coverity description

diff --git a/ci/images/README.md b/ci/images/README.md
index 1c72591d4f5a55663aa9311cce72e69eb1c1a40d..531c70c58d9e2979e6ff7398ff3256a1e3af32f6 100644 (file)
--- a/ci/images/README.md
+++ b/ci/images/README.md
@@ -6,10 +6,19 @@
 
 The main image used by shared runners to execute most CI builds and tests.
 
+### debian-11-coverity
+
+A stripped down version of `debian-11`. It only contains build (not test)
+dependencies of `kresd`. It also contains the `cov-build` tool for generating
+inputs for [Coverity Scan](https://scan.coverity.com/).
+
+It is used by the `coverity` CI job to generate and send data to Coverity Scan
+for analysis.
+
 ### debian-bullseye
 
-Used to serve the same as `debian-11`. As of 2022-03-09, it is still used by
-some jobs (linters).
+Used to serve the same purpose as `debian-11`. As of 2022-03-09, it is still
+used by some jobs (linters).
 
 ### lxc-debian-11