1 files changed, 10 insertions, 0 deletions
diff --git a/src/exec.zig b/src/exec.zig
index b8312a21..953ae0f3 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -249,6 +249,16 @@ pub fn saveFile(p: *Pardes, id: usize) void {
     const pane = p.panes[id] orelse return;
     const f = if (pane.file) |*file| file else return;
     if (f.output != null) return; // nothing behind it yet: saveTo, with a path
+    // Its file changed on disk under these edits: once, as acme's Put says
+    // "modified since last read" (exec.c:577), and the next Save writes.
+    if (f.disk_newer != null) {
+        if (!f.disk_newer_warned) {
+            f.disk_newer_warned = true;
+            var said: [Pardes.SavePath.cap + 64]u8 = undefined;
+            return p.reportFailure(id, std.fmt.bufPrint(&said, "{s} modified on disk since read (Save again to overwrite)", .{f.path}) catch "modified on disk since read (Save again to overwrite)");
+        }
+        f.disk_newer = null;
+    }
     p.emit(.{ .save_file = .{ .pane = @intCast(id) } });
 }