Refactor overlay-headers.sh for better readability

Updated comments for clarity and improved error handling in overlay-headers.sh.

Author: ChrisDryden

util/gnu-patches/tests_tail_overlay_headers.patch

@@ -1,49 +1 @@
---- gnu.orig/tests/tail/overlay-headers.sh	2025-12-07 23:20:20.566198669 +0100
-+++ gnu/tests/tail/overlay-headers.sh	2025-12-07 23:20:20.570198688 +0100
-@@ -56,26 +56,39 @@
 
- kill -0 $pid || fail=1
-
--# Wait for 5 initial lines
--retry_delay_ wait4lines_ .1 6 5 || fail=1
-+# Wait for 5 initial lines (2 headers + 2 content lines + 1 blank)
-+retry_delay_ wait4lines_ .1 6 5 || { echo "Failed waiting for initial 5 lines"; fail=1; }
-+
-+echo "=== After initial wait, line count: $(countlines_) ==="
-+echo "=== Initial output: ===" && cat out && echo "=== End initial output ==="
-
- # Suspend tail so single read() caters for multiple inotify events
--kill -STOP $pid || fail=1
-+kill -STOP $pid || { echo "Failed to STOP tail process"; fail=1; }
-
- # Interleave writes to files to generate overlapping inotify events
- echo line >> file1 || framework_failure_
- echo line >> file2 || framework_failure_
- echo line >> file1 || framework_failure_
- echo line >> file2 || framework_failure_
-+echo "=== Files written, resuming tail ==="
-
- # Resume tail processing
--kill -CONT $pid || fail=1
-+kill -CONT $pid || { echo "Failed to CONT tail process"; fail=1; }
-
--# Wait for 8 more lines
--retry_delay_ wait4lines_ .1 6 13 || fail=1
-+# Wait for 8 more lines (should total 13)
-+retry_delay_ wait4lines_ .1 6 13 || { echo "Failed waiting for 13 total lines"; fail=1; }
-
- kill $sleep && wait || framework_failure_
-
--test "$(countlines_)" = 13 || fail=1
-+final_count=$(countlines_)
-+echo "=== Final line count: $final_count (expected 13) ==="
-+
-+if test "$final_count" != 13; then
-+  echo "=== FAILURE: Expected 13 lines, got $final_count ==="
-+  echo "=== Full output content: ==="
-+  cat -A out
-+  echo "=== End output content ==="
-+  fail=1
-+fi
-
- Exit $fail