just-mr gc-repo: support drop only

As opposed to the regular CAS/cache, for the git repository implicit
in the repository cache we cannot guarantee that data from older
generation is always promoted via hard links. Therefore, a certain
amount of data can be duplicated between the repo-cache generations.
In order to allow compacting storage to the minimum, add an option
to gc-repo to only remove the older generation, without rotating.

2 files changed, 22 insertions, 1 deletions

diff --git a/src/other_tools/just_mr/cli.hpp b/src/other_tools/just_mr/cli.hpp
index 0c3e63a9..96f7cba2 100644
--- a/src/other_tools/just_mr/cli.hpp
+++ b/src/other_tools/just_mr/cli.hpp
@@ -85,6 +85,10 @@ struct MultiRepoUpdateArguments {
     std::vector<std::string> repos_to_update;
 };
 
+struct MultiRepoGcArguments {
+    bool drop_only{false};
+};
+
 struct MultiRepoJustSubCmdsArguments {
     std::optional<std::string> subcmd_name{std::nullopt};
     std::vector<std::string> additional_just_args;
@@ -124,6 +128,7 @@ struct CommandLineArguments {
     MultiRepoSetupArguments setup;
     MultiRepoFetchArguments fetch;
     MultiRepoUpdateArguments update;
+    MultiRepoGcArguments gc;
     MultiRepoJustSubCmdsArguments just_cmd;
     MultiRepoRemoteAuthArguments auth;
     ForwardOnlyArguments launch_fwd;
@@ -338,6 +343,14 @@ static inline void SetupMultiRepoUpdateArguments(
         ->type_name("");
 }
 
+static inline void SetupMultiRepoGcArguments(
+    gsl::not_null<CLI::App*> const& app,
+    gsl::not_null<MultiRepoGcArguments*> const& clargs) {
+    app->add_flag("--drop-only",
+                  clargs->drop_only,
+                  "Only drop old repository generations");
+}
+
 static inline auto SetupMultiRepoRemoteAuthArguments(
     gsl::not_null<CLI::App*> const& app,
     gsl::not_null<MultiRepoRemoteAuthArguments*> const& authargs) {
diff --git a/src/other_tools/just_mr/main.cpp b/src/other_tools/just_mr/main.cpp
index 28d4669f..d65cbb50 100644
--- a/src/other_tools/just_mr/main.cpp
+++ b/src/other_tools/just_mr/main.cpp
@@ -82,6 +82,13 @@ void SetupUpdateCommandArguments(
     SetupMultiRepoUpdateArguments(app, &clargs->update);
 }
 
+/// \brief Setup arguments for subcommand "just-mr gc-repo".
+void SetupUpdateGcArguments(
+    gsl::not_null<CLI::App*> const& app,
+    gsl::not_null<CommandLineArguments*> const& clargs) {
+    SetupMultiRepoGcArguments(app, &clargs->gc);
+}
+
 /// \brief Setup arguments for subcommand "just-mr setup" and
 /// "just-mr setup-env".
 void SetupSetupCommandArguments(
@@ -133,6 +140,7 @@ void SetupSetupCommandArguments(
     SetupSetupCommandArguments(cmd_setup_env, &clargs);
     SetupFetchCommandArguments(cmd_fetch, &clargs);
     SetupUpdateCommandArguments(cmd_update, &clargs);
+    SetupUpdateGcArguments(cmd_gc_repo, &clargs);
 
     // for 'just' calls, allow extra arguments
     cmd_do->allow_extras();
@@ -336,7 +344,7 @@ auto main(int argc, char* argv[]) -> int {
 
         if (arguments.cmd == SubCommand::kGcRepo) {
             return RepositoryGarbageCollector::TriggerGarbageCollection(
-                       *native_storage_config)
+                       *native_storage_config, arguments.gc.drop_only)
                        ? kExitSuccess
                        : kExitBuiltinCommandFailure;
         }