Add Git object hashing to the store layer

Part of RFC 133

Extracted from our old IPFS branches.

Co-Authored-By: Matthew Bauer <mjbauer95@gmail.com>
Co-Authored-By: Carlo Nucera <carlo.nucera@protonmail.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
Co-authored-by: Florian Klink <flokli@flokli.de>

src/libutil/file-content-address.cc

@@ -1,16 +1,53 @@
 #include "file-content-address.hh"
 #include "archive.hh"
+#include "git.hh"
 
 namespace nix {
 
-FileIngestionMethod parseFileIngestionMethod(std::string_view input)
+static std::optional<FileSerialisationMethod> parseFileSerialisationMethodOpt(std::string_view input)
 {
     if (input == "flat") {
-        return FileIngestionMethod::Flat;
+        return FileSerialisationMethod::Flat;
     } else if (input == "nar") {
-        return FileIngestionMethod::Recursive;
+        return FileSerialisationMethod::Recursive;
     } else {
-        throw UsageError("Unknown file ingestion method '%s', expect `flat` or `nar`");
+        return std::nullopt;
+    }
+}
+
+FileSerialisationMethod parseFileSerialisationMethod(std::string_view input)
+{
+    auto ret = parseFileSerialisationMethodOpt(input);
+    if (ret)
+        return *ret;
+    else
+        throw UsageError("Unknown file serialiation method '%s', expect `flat` or `nar`");
+}
+
+
+FileIngestionMethod parseFileIngestionMethod(std::string_view input)
+{
+    if (input == "git") {
+        return FileIngestionMethod::Git;
+    } else {
+        auto ret = parseFileSerialisationMethodOpt(input);
+        if (ret)
+            return static_cast<FileIngestionMethod>(*ret);
+        else
+            throw UsageError("Unknown file ingestion method '%s', expect `flat`, `nar`, or `git`");
+    }
+}
+
+
+std::string_view renderFileSerialisationMethod(FileSerialisationMethod method)
+{
+    switch (method) {
+    case FileSerialisationMethod::Flat:
+        return "flat";
+    case FileSerialisationMethod::Recursive:
+        return "nar";
+    default:
+        assert(false);
     }
 }
 
@@ -19,9 +56,11 @@ std::string_view renderFileIngestionMethod(FileIngestionMethod method)
 {
     switch (method) {
     case FileIngestionMethod::Flat:
-        return "flat";
     case FileIngestionMethod::Recursive:
-        return "nar";
+        return renderFileSerialisationMethod(
+            static_cast<FileSerialisationMethod>(method));
+    case FileIngestionMethod::Git:
+        return "git";
     default:
         abort();
     }
@@ -31,14 +70,14 @@ std::string_view renderFileIngestionMethod(FileIngestionMethod method)
 void dumpPath(
     SourceAccessor & accessor, const CanonPath & path,
     Sink & sink,
-    FileIngestionMethod method,
+    FileSerialisationMethod method,
     PathFilter & filter)
 {
     switch (method) {
-    case FileIngestionMethod::Flat:
+    case FileSerialisationMethod::Flat:
         accessor.readFile(path, sink);
         break;
-    case FileIngestionMethod::Recursive:
+    case FileSerialisationMethod::Recursive:
         accessor.dumpPath(path, sink, filter);
         break;
     }
@@ -48,13 +87,13 @@ void dumpPath(
 void restorePath(
     const Path & path,
     Source & source,
-    FileIngestionMethod method)
+    FileSerialisationMethod method)
 {
     switch (method) {
-    case FileIngestionMethod::Flat:
+    case FileSerialisationMethod::Flat:
         writeFile(path, source);
         break;
-    case FileIngestionMethod::Recursive:
+    case FileSerialisationMethod::Recursive:
         restorePath(path, source);
         break;
     }
@@ -63,7 +102,7 @@ void restorePath(
 
 HashResult hashPath(
     SourceAccessor & accessor, const CanonPath & path,
-    FileIngestionMethod method, HashAlgorithm ha,
+    FileSerialisationMethod method, HashAlgorithm ha,
     PathFilter & filter)
 {
     HashSink sink { ha };
@@ -71,4 +110,20 @@ HashResult hashPath(
     return sink.finish();
 }
 
+
+Hash hashPath(
+    SourceAccessor & accessor, const CanonPath & path,
+    FileIngestionMethod method, HashAlgorithm ht,
+    PathFilter & filter)
+{
+    switch (method) {
+    case FileIngestionMethod::Flat:
+    case FileIngestionMethod::Recursive:
+        return hashPath(accessor, path, (FileSerialisationMethod) method, ht, filter).first;
+    case FileIngestionMethod::Git:
+        return git::dumpHash(ht, accessor, path, filter).hash;
+    }
+
+}
+
 }