Add a "root" parameter to local stores

This makes it easier to create a diverted store, i.e.

  NIX_REMOTE="local?root=/tmp/root"

instead of

  NIX_REMOTE="local?real=/tmp/root/nix/store&state=/tmp/root/nix/var/nix" NIX_LOG_DIR=/tmp/root/nix/var/log

4 files changed, 7 insertions, 3 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 10ae574f9e..08a7fd91dd 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2910,7 +2910,7 @@ Path DerivationGoal::openLogFile()
     string baseName = baseNameOf(drvPath);
 
     /* Create a log file. */
-    Path dir = (format("%1%/%2%/%3%/") % settings.nixLogDir % drvsLogDir % string(baseName, 0, 2)).str();
+    Path dir = (format("%1%/%2%/%3%/") % worker.store.logDir % drvsLogDir % string(baseName, 0, 2)).str();
     createDirs(dir);
 
     Path logFileName = (format("%1%/%2%%3%")
diff --git a/src/libstore/local-fs-store.cc b/src/libstore/local-fs-store.cc
index b1b9dc29e4..c6ed8f746c 100644
--- a/src/libstore/local-fs-store.cc
+++ b/src/libstore/local-fs-store.cc
@@ -7,7 +7,9 @@ namespace nix {
 
 LocalFSStore::LocalFSStore(const Params & params)
     : Store(params)
-    , stateDir(get(params, "state", settings.nixStateDir))
+    , rootDir(get(params, "root"))
+    , stateDir(canonPath(get(params, "state", rootDir != "" ? rootDir + "/nix/var/nix" : settings.nixStateDir)))
+    , logDir(canonPath(get(params, "log", rootDir != "" ? rootDir + "/nix/var/log/nix" : settings.nixLogDir)))
 {
 }
 
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index f961091230..bc03c53740 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -38,7 +38,7 @@ namespace nix {
 
 LocalStore::LocalStore(const Params & params)
     : LocalFSStore(params)
-    , realStoreDir(get(params, "real", storeDir))
+    , realStoreDir(get(params, "real", rootDir != "" ? rootDir + "/nix/store" : storeDir))
     , dbDir(stateDir + "/db")
     , linksDir(realStoreDir + "/.links")
     , reservedPath(dbDir + "/reserved")
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 0b80312d63..f80a06aaf8 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -491,7 +491,9 @@ protected:
 class LocalFSStore : public Store
 {
 public:
+    const Path rootDir;
     const Path stateDir;
+    const Path logDir;
 
     LocalFSStore(const Params & params);