From bba4e6b061f53cbc77d47408468f9bc0f534281b Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 18 Feb 2025 11:22:00 +0100
Subject: [PATCH] Restore detailed Nix CLI version

... as intended.

Requirements:
- don't build fresh libraries for each git commit
- have git commit in the CLI

Bug:
- echo ${version} went into the wrong file => use the fact that it's
  a symlink, not just for reading but also for writing.
---
 src/libstore/globals.cc |  2 +-
 src/libstore/globals.hh | 10 +++++++++-
 src/nix/main.cc         |  2 ++
 src/nix/meson.build     |  3 +++
 src/nix/package.nix     |  6 +++---
 5 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index e908fc81f..d7c000dfa 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -242,7 +242,7 @@ Path Settings::getDefaultSSLCertFile()
     return "";
 }
 
-const std::string nixVersion = PACKAGE_VERSION;
+std::string nixVersion = PACKAGE_VERSION;
 
 NLOHMANN_JSON_SERIALIZE_ENUM(SandboxMode, {
     {SandboxMode::smEnabled, true},
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index d0e6f33d4..f62644ff1 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -1248,7 +1248,15 @@ void loadConfFile(AbstractConfig & config);
 // Used by the Settings constructor
 std::vector<Path> getUserConfigFiles();
 
-extern const std::string nixVersion;
+/**
+ * The version of Nix itself.
+ *
+ * This is not `const`, so that the Nix CLI can provide a more detailed version
+ * number including the git revision, without having to "re-compile" the entire
+ * set of Nix libraries to include that version, even when those libraries are
+ * not affected by the change.
+ */
+extern std::string nixVersion;
 
 /**
  * @param loadConfig Whether to load configuration from `nix.conf`, `NIX_CONFIG`, etc. May be disabled for unit tests.
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 80ef53084..f8d0100ac 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -557,6 +557,8 @@ void mainWrapped(int argc, char * * argv)
 
 int main(int argc, char * * argv)
 {
+    // The CLI has a more detailed version than the libraries; see nixVersion.
+    nix::nixVersion = NIX_CLI_VERSION;
 #ifndef _WIN32
     // Increase the default stack size for the evaluator and for
     // libstdc++'s std::regex.
diff --git a/src/nix/meson.build b/src/nix/meson.build
index 25aa1e668..398750498 100644
--- a/src/nix/meson.build
+++ b/src/nix/meson.build
@@ -35,6 +35,9 @@ subdir('nix-meson-build-support/windows-version')
 
 configdata = configuration_data()
 
+# The CLI has a more detailed version string than the libraries; see `nixVersion`
+configdata.set_quoted('NIX_CLI_VERSION', meson.project_version())
+
 fs = import('fs')
 
 bindir = get_option('bindir')
diff --git a/src/nix/package.nix b/src/nix/package.nix
index 6e59adc38..bb90be1ef 100644
--- a/src/nix/package.nix
+++ b/src/nix/package.nix
@@ -92,11 +92,11 @@ mkMesonExecutable (finalAttrs: {
   ];
 
   preConfigure =
-    # "Inline" .version so it's not a symlink, and includes the suffix.
-    # Do the meson utils, without modification.
+    # Update the repo-global .version file.
+    # Symlink ./.version points there, but by default only workDir is writable.
     ''
       chmod u+w ./.version
-      echo ${version} > ../../../.version
+      echo ${version} > ./.version
     '';
 
   mesonFlags = [