git tree repository: Creating absent roots should not run the command

Also extended absent-roots test with this scenario.

2 files changed, 41 insertions, 1 deletions

diff --git a/src/other_tools/root_maps/tree_id_git_map.cpp b/src/other_tools/root_maps/tree_id_git_map.cpp
index ce2fe5e5..752f224d 100644
--- a/src/other_tools/root_maps/tree_id_git_map.cpp
+++ b/src/other_tools/root_maps/tree_id_git_map.cpp
@@ -96,7 +96,16 @@ auto CreateTreeIdGitMap(
                            auto logger,
                            auto /*unused*/,
                            auto const& key) {
-        // first, check whether tree exists already in CAS
+        // if root is absent, no work needs to be done
+        if (key.absent) {
+            auto root = nlohmann::json::array(
+                {key.ignore_special ? FileRoot::kGitTreeIgnoreSpecialMarker
+                                    : FileRoot::kGitTreeMarker,
+                 key.hash});
+            (*setter)(std::pair(std::move(root), false));
+            return;
+        }
+        // check whether tree exists already in CAS
         // ensure Git cache
         // define Git operation to be done
         GitOpKey op_key = {.params =
diff --git a/test/end-to-end/just-mr/absent-roots.sh b/test/end-to-end/just-mr/absent-roots.sh
index 7f3154a6..ad4846e1 100644
--- a/test/end-to-end/just-mr/absent-roots.sh
+++ b/test/end-to-end/just-mr/absent-roots.sh
@@ -109,4 +109,35 @@ test $(jq -r '.repositories.test.workspace_root | length' "${CONF}") = 2
 # Check the tree was correctly set via 'just serve' remote
 test "$(jq -r '.repositories.test.workspace_root[1]' "${CONF}")" = "${GIT_ROOT_ID}"
 
+# Now check that an absent git tree repository works without running the command
+rm -rf "${LBR}"
+
+cat > repos.json <<EOF
+{ "repositories":
+  { "test":
+    { "repository":
+      { "type": "git tree"
+      , "id": "${GIT_ROOT_ID}"
+      , "cmd": ["non_existent_script.sh"]
+      , "pragma": {"absent": true}
+      }
+    }
+  }
+}
+EOF
+echo "Repository configuration:"
+cat repos.json
+
+# Compute the repository configuration
+CONF=$("${JUST_MR}" --norc --local-build-root "${LBR}" --remote-serve-address localhost:${PORT} setup)
+cat "${CONF}"
+echo
+
+# Check that an absent root was created
+test "$(jq -r '.repositories.test.workspace_root[0]' "${CONF}")" = "git tree"
+test $(jq -r '.repositories.test.workspace_root | length' "${CONF}") = 2
+
+# Check the tree was correctly set via 'just serve' remote
+test "$(jq -r '.repositories.test.workspace_root[1]' "${CONF}")" = "${GIT_ROOT_ID}"
+
 echo OK