1 files changed, 8 insertions, 1 deletions
diff --git a/src/libstore/profiles.hh b/src/libstore/profiles.hh
index be55a65d4..d100c970c 100644
--- a/src/libstore/profiles.hh
+++ b/src/libstore/profiles.hh
@@ -11,7 +11,7 @@ namespace nix {
 class StorePath;
 
 
-typedef unsigned int GenerationNumber;
+typedef uint64_t GenerationNumber;
 
 struct Generation
 {
@@ -46,6 +46,13 @@ void deleteGenerationsOlderThan(const Path & profile, const string & timeSpec, b
 
 void switchLink(Path link, Path target);
 
+/* Roll back a profile to the specified generation, or to the most
+   recent one older than the current. */
+void switchGeneration(
+    const Path & profile,
+    std::optional<GenerationNumber> dstGen,
+    bool dryRun);
+
 /* Ensure exclusive access to a profile.  Any command that modifies
    the profile first acquires this lock. */
 void lockProfile(PathLocks & lock, const Path & profile);