just-mr: Implement 'absent' roots

...via an 'absent' pragma in repository descriptions.

For 'git'-type repositories, first interrogates a 'just serve'
remote, if given, before reverting to fetching from the network.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/other_tools/root_maps/distdir_git_map.hpp b/src/other_tools/root_maps/distdir_git_map.hpp
index c440253b..4c282157 100644
--- a/src/other_tools/root_maps/distdir_git_map.hpp
+++ b/src/other_tools/root_maps/distdir_git_map.hpp
@@ -27,10 +27,12 @@ struct DistdirInfo {
     std::shared_ptr<std::vector<ArchiveContent>> repos_to_fetch;
     // name of repository for which work is done; used in progress reporting
     std::string origin;
+    // create an absent root
+    bool absent{}; /* key */
 
     [[nodiscard]] auto operator==(const DistdirInfo& other) const noexcept
         -> bool {
-        return content_id == other.content_id;
+        return content_id == other.content_id and absent == other.absent;
     }
 };
 
@@ -51,7 +53,10 @@ template <>
 struct hash<DistdirInfo> {
     [[nodiscard]] auto operator()(const DistdirInfo& dd) const noexcept
         -> std::size_t {
-        return std::hash<std::string>{}(dd.content_id);
+        size_t seed{};
+        hash_combine<std::string>(&seed, dd.content_id);
+        hash_combine<bool>(&seed, dd.absent);
+        return seed;
     }
 };
 }  // namespace std