just install-cas: add option --archive

Trees are first-class objects for justbuild. To allow interoperation
with other tools, it is necessary to provide those objects in a
standard format; for directories, those are archives. Hence procive
a corresponding option.

4 files changed, 36 insertions, 6 deletions

diff --git a/share/man/just.1.md b/share/man/just.1.md
index de84f44b..812cd33f 100644
--- a/share/man/just.1.md
+++ b/share/man/just.1.md
@@ -496,9 +496,16 @@ Install path for the artifact. Refer to **`install-cas`** section for more
 details.  
 Supported by: install-cas.
 
+**`--archive`**  
+Instead of installing the requested tree, install an archive with the
+content of the tree. It is a user error to specify **`--archive`** and
+not request a tree.  
+Supported by: install-cas.
+
 **`--raw-tree`**  
 When installing a tree to stdout, i.e., when no option **`-o`** is given,
-dump the raw tree rather than a pretty-printed version.  
+dump the raw tree rather than a pretty-printed version. This option is
+ignored if **`--archive`** is given.  
 Supported by: install-cas.
 
 **`-P`**, **`--sub-object-path`** *`PATH`*  
diff --git a/src/buildtool/common/cli.hpp b/src/buildtool/common/cli.hpp
index e7f78201..7ede3217 100644
--- a/src/buildtool/common/cli.hpp
+++ b/src/buildtool/common/cli.hpp
@@ -138,6 +138,7 @@ struct FetchArguments {
     std::optional<std::filesystem::path> sub_path{};
     bool remember{false};
     bool raw_tree{};
+    bool archive{};
 };
 
 /// \brief Arguments required for running from graph file.
@@ -600,9 +601,11 @@ static inline auto SetupFetchArguments(
            "tree).")
         ->type_name("PATH");
 
+    app->add_flag(
+        "--archive", clargs->archive, "Dump the tree as a single archive.");
     app->add_flag("--raw-tree",
                   clargs->raw_tree,
-                  "Dump raw tree object (omit pretty printing)");
+                  "Dump raw tree object (omit pretty printing).");
 
     app->add_flag(
         "--remember", clargs->remember, "Copy object to local CAS first");
diff --git a/src/buildtool/main/TARGETS b/src/buildtool/main/TARGETS
index 626fe9f2..b15ef25a 100644
--- a/src/buildtool/main/TARGETS
+++ b/src/buildtool/main/TARGETS
@@ -119,6 +119,7 @@
     , ["src/buildtool/logging", "log_level"]
     , ["src/buildtool/logging", "logging"]
     , ["src/buildtool/execution_api/utils", "subobject"]
+    , "archive"
     ]
   }
 , "add_to_cas":
@@ -286,7 +287,10 @@
   , "name": ["archive"]
   , "hdrs": ["archive.hpp"]
   , "srcs": ["archive.cpp"]
-  , "deps": [["src/buildtool/common", "common"]]
+  , "deps":
+    [ ["src/buildtool/common", "common"]
+    , ["src/buildtool/execution_api/common", "common"]
+    ]
   , "stage": ["src", "buildtool", "main"]
   , "private-deps":
     [ ["", "libarchive"]
diff --git a/src/buildtool/main/install_cas.cpp b/src/buildtool/main/install_cas.cpp
index ed989883..e6bb9128 100644
--- a/src/buildtool/main/install_cas.cpp
+++ b/src/buildtool/main/install_cas.cpp
@@ -23,6 +23,7 @@
 #include "src/buildtool/logging/logger.hpp"
 #ifndef BOOTSTRAP_BUILD_TOOL
 #include "src/buildtool/execution_api/utils/subobject.hpp"
+#include "src/buildtool/main/archive.hpp"
 #endif
 
 namespace {
@@ -96,7 +97,9 @@ auto FetchAndInstallArtifacts(
         }
     }
 
+    std::optional<std::filesystem::path> out{};
     if (clargs.output_path) {
+        // Compute output location and create parent directories
         auto output_path = (*clargs.output_path / "").parent_path();
         if (FileSystemManager::IsDirectory(output_path)) {
             output_path /= object_info.digest.hash();
@@ -108,8 +111,21 @@ auto FetchAndInstallArtifacts(
                         output_path.parent_path().string());
             return false;
         }
-        if (not api->RetrieveToPaths(
-                {object_info}, {output_path}, alternative_api)) {
+        out = output_path;
+    }
+
+    if (clargs.archive) {
+        if (object_info.type != ObjectType::Tree) {
+            Logger::Log(LogLevel::Error,
+                        "Archive requested on non-tree {}",
+                        object_info.ToString());
+            return false;
+        }
+        return GenerateArchive(api, object_info, out);
+    }
+
+    if (out) {
+        if (not api->RetrieveToPaths({object_info}, {*out}, alternative_api)) {
             Logger::Log(LogLevel::Error, "failed to retrieve artifact.");
             return false;
         }
@@ -117,7 +133,7 @@ auto FetchAndInstallArtifacts(
         Logger::Log(LogLevel::Info,
                     "artifact {} was installed to {}",
                     object_info.ToString(),
-                    output_path.string());
+                    out->string());
     }
     else {  // dump to stdout
         if (not api->RetrieveToFds(