Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libfetchers/git-utils.hh

@@ -0,0 +1,118 @@
+#pragma once
+
+#include "filtering-source-accessor.hh"
+#include "fs-sink.hh"
+
+namespace nix {
+
+namespace fetchers { struct PublicKey; }
+
+/**
+ * A sink that writes into a Git repository. Note that nothing may be written
+ * until `flush()` is called.
+ */
+struct GitFileSystemObjectSink : ExtendedFileSystemObjectSink
+{
+    /**
+     * Flush builder and return a final Git hash.
+     */
+    virtual Hash flush() = 0;
+};
+
+struct GitRepo
+{
+    virtual ~GitRepo()
+    { }
+
+    static ref<GitRepo> openRepo(const std::filesystem::path & path, bool create = false, bool bare = false);
+
+    virtual uint64_t getRevCount(const Hash & rev) = 0;
+
+    virtual uint64_t getLastModified(const Hash & rev) = 0;
+
+    virtual bool isShallow() = 0;
+
+    /* Return the commit hash to which a ref points. */
+    virtual Hash resolveRef(std::string ref) = 0;
+
+    virtual void setRemote(const std::string & name, const std::string & url) = 0;
+
+    /**
+     * Info about a submodule.
+     */
+    struct Submodule
+    {
+        CanonPath path;
+        std::string url;
+        std::string branch;
+    };
+
+    struct WorkdirInfo
+    {
+        bool isDirty = false;
+
+        /* The checked out commit, or nullopt if there are no commits
+           in the repo yet. */
+        std::optional<Hash> headRev;
+
+        /* All files in the working directory that are unchanged,
+           modified or added, but excluding deleted files. */
+        std::set<CanonPath> files;
+
+        /* The submodules listed in .gitmodules of this workdir. */
+        std::vector<Submodule> submodules;
+    };
+
+    virtual WorkdirInfo getWorkdirInfo() = 0;
+
+    /* Get the ref that HEAD points to. */
+    virtual std::optional<std::string> getWorkdirRef() = 0;
+
+    /**
+     * Return the submodules of this repo at the indicated revision,
+     * along with the revision of each submodule.
+     */
+    virtual std::vector<std::tuple<Submodule, Hash>> getSubmodules(const Hash & rev, bool exportIgnore) = 0;
+
+    virtual std::string resolveSubmoduleUrl(const std::string & url) = 0;
+
+    virtual bool hasObject(const Hash & oid) = 0;
+
+    virtual ref<SourceAccessor> getAccessor(const Hash & rev, bool exportIgnore) = 0;
+
+    virtual ref<SourceAccessor> getAccessor(const WorkdirInfo & wd, bool exportIgnore, MakeNotAllowedError makeNotAllowedError) = 0;
+
+    virtual ref<GitFileSystemObjectSink> getFileSystemObjectSink() = 0;
+
+    virtual void flush() = 0;
+
+    virtual void fetch(
+        const std::string & url,
+        const std::string & refspec,
+        bool shallow) = 0;
+
+    /**
+     * Verify that commit `rev` is signed by one of the keys in
+     * `publicKeys`. Throw an error if it isn't.
+     */
+    virtual void verifyCommit(
+        const Hash & rev,
+        const std::vector<fetchers::PublicKey> & publicKeys) = 0;
+
+    /**
+     * Given a Git tree hash, compute the hash of its NAR
+     * serialisation. This is memoised on-disk.
+     */
+    virtual Hash treeHashToNarHash(const Hash & treeHash) = 0;
+
+    /**
+     * If the specified Git object is a directory with a single entry
+     * that is a directory, return the ID of that object.
+     * Otherwise, return the passed ID unchanged.
+     */
+    virtual Hash dereferenceSingletonDirectory(const Hash & oid) = 0;
+};
+
+ref<GitRepo> getTarballCache();
+
+}