commit rustfmt stump in `x t tidy` even on `check`

If checking succeeded, it's equivalent to successfully formatting.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/bootstrap/src/core/build_steps/format.rs b/src/bootstrap/src/core/build_steps/format.rs
index 6641c4b4e13..9da8b27a917 100644
--- a/src/bootstrap/src/core/build_steps/format.rs
+++ b/src/bootstrap/src/core/build_steps/format.rs
@@ -336,7 +336,10 @@ pub fn format(build: &Builder<'_>, check: bool, all: bool, paths: &[PathBuf]) {
         crate::exit!(1);
     }
 
-    if !check {
-        update_rustfmt_version(build);
-    }
+    // Update `build/.rustfmt-stamp`, allowing this code to ignore files which have not been changed
+    // since last merge.
+    //
+    // NOTE: Because of the exit above, this is only reachable if formatting / format checking
+    // succeeded. So we are not commiting the version if formatting was not good.
+    update_rustfmt_version(build);
 }