[PATCH datacenter-manager v2] add `make coverage` build target

[Lukas Wagner <l.wagner@proxmox.com>]

This uses the `tarpaulin` tool to generate a test coverage report in the
'./coverage' directory.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>
---

Notes:
    `tarpaulin` is not packaged for Debian at the moment, so one has to
    install it via `cargo install --locked cargo-tarpaulin`.
    
    We could consider packaging it ourselves, however, last time I checked
    some of the (transitive) dependencies were a bit inconvenient, so maybe
    we'd have to vendor them, similar to how we do it with `proxmox-biome`.
    
    Changes from v1:
    
     - fix grammar mistake in commit message
     - remove trailing space in makefile recipe

 .gitignore     |  2 ++
 Makefile       |  6 ++++++
 tarpaulin.toml | 22 ++++++++++++++++++++++
 3 files changed, 30 insertions(+)
 create mode 100644 tarpaulin.toml

diff --git a/.gitignore b/.gitignore
index eb4a27ea..8de2bdad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,3 +20,5 @@
 /ui/target
 Cargo.lock
 proxmox-datacenter-manager-[0-9].*/
+
+/coverage
diff --git a/Makefile b/Makefile
index 537e6faa..48a5d112 100644
--- a/Makefile
+++ b/Makefile
@@ -148,6 +148,7 @@ upload-ui:
 distclean: clean
 clean: clean-deb
 	$(CARGO) clean
+	rm -rf ./coverage
 	$(MAKE) -C docs clean
 	$(MAKE) -C $(COMPLETION_DIR) clean
 	$(MAKE) -C $(UI_DIR) clean
@@ -179,3 +180,8 @@ tidy:
 	$(CARGO) fmt
 	$(MAKE) -C $(UI_DIR) tidy
 
+
+.PHONY: coverage
+coverage:
+	$(CARGO) tarpaulin
+	@echo "\nCoverage report in ./coverage/tarpaulin-report.html"
diff --git a/tarpaulin.toml b/tarpaulin.toml
new file mode 100644
index 00000000..01740418
--- /dev/null
+++ b/tarpaulin.toml
@@ -0,0 +1,22 @@
+[test_config]
+
+# Skip the clean step and proceed without cleaning the target directory.
+skip-clean = true
+
+# Count hits for coverage, useful for more detailed reporting.
+count = true
+
+# List of file paths to exclude from testing.
+exclude-files = [
+    "proxmox-datacenter-manager*",
+    "ui/*"
+]
+
+# Specify the engine to use for collecting coverage (default: "trace").
+engine = "Llvm"
+
+[report]
+# Directory to output coverage files and reports.
+output-dir = "./coverage"
+
+out = ["Html"]
-- 
2.47.3