From 3eb621750848e0e6b30e5a79f76afbb096bb6c8a Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Wed, 27 Jul 2016 17:47:18 +0200
Subject: [PATCH] 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
---
 src/libstore/build.cc          | 2 +-
 src/libstore/local-fs-store.cc | 4 +++-
 src/libstore/local-store.cc    | 2 +-
 src/libstore/store-api.hh      | 2 ++
 src/nix-store/nix-store.cc     | 8 ++++++--
 5 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 10ae574f9..08a7fd91d 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 b1b9dc29e..c6ed8f746 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 f96109123..bc03c5374 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 0b80312d6..f80a06aaf 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);
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 8532101a1..e8b56f929 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -483,6 +483,10 @@ static void opReadLog(Strings opFlags, Strings opArgs)
 
     RunPager pager;
 
+    // FIXME: move getting logs into Store.
+    auto store2 = std::dynamic_pointer_cast<LocalFSStore>(store);
+    if (!store2) throw Error(format("store ‘%s’ does not support reading logs") % store->getUri());
+
     for (auto & i : opArgs) {
         Path path = useDeriver(store->followLinksToStorePath(i));
 
@@ -493,8 +497,8 @@ static void opReadLog(Strings opFlags, Strings opArgs)
 
             Path logPath =
                 j == 0
-                ? (format("%1%/%2%/%3%/%4%") % settings.nixLogDir % drvsLogDir % string(baseName, 0, 2) % string(baseName, 2)).str()
-                : (format("%1%/%2%/%3%") % settings.nixLogDir % drvsLogDir % baseName).str();
+                ? (format("%1%/%2%/%3%/%4%") % store2->logDir % drvsLogDir % string(baseName, 0, 2) % string(baseName, 2)).str()
+                : (format("%1%/%2%/%3%") % store2->logDir % drvsLogDir % baseName).str();
             Path logBz2Path = logPath + ".bz2";
 
             if (pathExists(logPath)) {