2 files changed, 78 insertions, 1 deletions
diff --git a/src/libexpr/primops/fetchgit.cc b/src/libexpr/primops/fetchgit.cc
new file mode 100644
index 0000000000..e2a545ee05
--- /dev/null
+++ b/src/libexpr/primops/fetchgit.cc
@@ -0,0 +1,77 @@
+#include "primops.hh"
+#include "eval-inline.hh"
+#include "download.hh"
+#include "store-api.hh"
+
+namespace nix {
+
+static void prim_fetchgit(EvalState & state, const Pos & pos, Value * * args, Value & v)
+{
+    // FIXME: cut&paste from fetch().
+    if (state.restricted) throw Error("‘fetchgit’ is not allowed in restricted mode");
+
+    std::string url;
+    std::string rev = "master";
+
+    state.forceValue(*args[0]);
+
+    if (args[0]->type == tAttrs) {
+
+        state.forceAttrs(*args[0], pos);
+
+        for (auto & attr : *args[0]->attrs) {
+            string name(attr.name);
+            if (name == "url")
+                url = state.forceStringNoCtx(*attr.value, *attr.pos);
+            else if (name == "rev")
+                rev = state.forceStringNoCtx(*attr.value, *attr.pos);
+            else
+                throw EvalError(format("unsupported argument ‘%1%’ to ‘fetchgit’, at %3%") % attr.name % attr.pos);
+        }
+
+        if (url.empty())
+            throw EvalError(format("‘url’ argument required, at %1%") % pos);
+
+    } else
+        url = state.forceStringNoCtx(*args[0], pos);
+
+    if (!isUri(url))
+        throw EvalError(format("‘%s’ is not a valid URI, at %s") % url % pos);
+
+    Path cacheDir = getCacheDir() + "/nix/git";
+
+    if (!pathExists(cacheDir)) {
+        createDirs(cacheDir);
+        runProgram("git", true, { "init", "--bare", cacheDir });
+    }
+
+    Activity act(*logger, lvlInfo, format("fetching Git repository ‘%s’") % url);
+
+    std::string localRef = "pid-" + std::to_string(getpid());
+    Path localRefFile = cacheDir + "/refs/heads/" + localRef;
+
+    runProgram("git", true, { "-C", cacheDir, "fetch", url, rev + ":" + localRef });
+
+    std::string commitHash = chomp(readFile(localRefFile));
+
+    unlink(localRefFile.c_str());
+
+    debug(format("got revision ‘%s’") % commitHash);
+
+    // FIXME: should pipe this, or find some better way to extract a
+    // revision.
+    auto tar = runProgram("git", true, { "-C", cacheDir, "archive", commitHash });
+
+    Path tmpDir = createTempDir();
+    AutoDelete delTmpDir(tmpDir, true);
+
+    runProgram("tar", true, { "x", "-C", tmpDir }, tar);
+
+    Path storePath = state.store->addToStore("git-export", tmpDir);
+
+    mkString(v, storePath, PathSet({storePath}));
+}
+
+static RegisterPrimOp r("__fetchgit", 1, prim_fetchgit);
+
+}
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index eed630517d..6e39330e40 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -313,7 +313,7 @@ bool isUri(const string & s)
     size_t pos = s.find("://");
     if (pos == string::npos) return false;
     string scheme(s, 0, pos);
-    return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel";
+    return scheme == "http" || scheme == "https" || scheme == "file" || scheme == "channel" || scheme == "git";
 }