no-mistakes(review): Make legacy-exclude cleanup command robust and hedge notice

Author: dmealing

docs/features/prerelease.md

@@ -177,7 +177,8 @@ unlinked too. A clone linked by an earlier version of the script holds those ent
 lines outside any block, which `unlink` cannot tell from a line a user added. `link` and
 `unlink` name such lines and print the one command that removes them, and leave them in
 place; `link` does not add a second copy inside the block while one is there. Run that
-command once no worktree of the clone is linked. Files that *are* tracked by definition
+command once no worktree of the clone is linked, after taking out of it any line you added
+yourself. Files that *are* tracked by definition
 (`pyproject.toml`, `pom.xml`) get a loud warning instead — there is no way to make an edit
 to a tracked file uncommittable, which is precisely why the detector in §5 exists.
 

tools/prerelease/prerelease-link.sh

@@ -267,15 +267,16 @@ legacy_exclude_notice() {
   [ -n "$ex" ] && [ -f "$ex" ] || return 0
   stale="$(written_exclude_paths | sort -u | grep -xF -f <(exclude_outside_lines "$ex") || true)"
   [ -n "$stale" ] || return 0
-  warn "$ex holds entries outside the managed block that name files this script writes"
-  warn "(left by an earlier version of it); unlink never removes a line it did not put in its block:"
+  warn "$ex holds entries outside the managed block that name files this script writes."
+  warn "They may have been left by an earlier version of this script; keep any you added yourself."
+  warn "unlink never removes a line it did not put in its block:"
   cmd="grep -vxF"
   while IFS= read -r p; do
     printf '    %s\n' "$p"
     cmd+=" -e $(printf '%q' "$p")"
   done <<< "$stale"
   say "once no work tree of this clone is linked, remove them with:"
-  say "  $cmd $(printf '%q' "$ex") > $(printf '%q' "$ex.tmp") && mv $(printf '%q' "$ex.tmp") $(printf '%q' "$ex")"
+  say "  { $cmd $(printf '%q' "$ex") || [ \$? -eq 1 ]; } > $(printf '%q' "$ex.tmp") && mv $(printf '%q' "$ex.tmp") $(printf '%q' "$ex")"
 }
 
 # Keep an untracked managed file out of commits without touching the shared .gitignore or any

tools/prerelease/test-prerelease-link.sh

@@ -173,13 +173,32 @@ check "link names the legacy line" 'grep -q "entries outside the managed block"
 unlink_project "$legacy"
 check "unlink names the legacy line" 'grep -q "entries outside the managed block" "$WORK/out" && grep -qx "    .npmrc" "$WORK/out"'
 check "unlink leaves the legacy line in place" 'grep -qxF .npmrc "$lcommon/info/exclude"'
-cleanup_cmd="$(sed -n 's/^    grep -vxF /grep -vxF /p' "$WORK/out")"
+cleanup_command() { sed -n 's/^    { grep -vxF /{ grep -vxF /p' "$WORK/out"; }
+cleanup_cmd="$(cleanup_command)"
 check "the notice carries one cleanup command" '[ "$(printf "%s\n" "$cleanup_cmd" | grep -c .)" = 1 ]'
 eval "$cleanup_cmd"
 check "the printed cleanup command removes the legacy line" '! grep -qxF .npmrc "$lcommon/info/exclude"'
 unlink_project "$legacy"
 check "with no legacy line left, unlink prints no notice" '! grep -q "entries outside the managed block" "$WORK/out"'
 
+# A clone made without git's templates had its exclude file created by the earlier script, so
+# the legacy line is all it holds. The printed command must still remove it: `grep -v` that
+# selects nothing exits 1, which is not a failure here.
+bare="$WORK/bare-legacy"
+git init -q "$bare"
+cp "$WORK/main/package.json" "$bare/package.json"
+git -C "$bare" add -A && git -C "$bare" commit -q -m init
+bcommon="$(git -C "$bare" rev-parse --git-common-dir)"
+case "$bcommon" in /*) ;; *) bcommon="$bare/$bcommon" ;; esac
+printf '.npmrc\n' > "$bcommon/info/exclude"
+link "$bare" || fail "link over an exclude file holding only the legacy line failed: $(tail -5 "$WORK/out")"
+unlink_project "$bare"
+cleanup_cmd="$(cleanup_command)"
+check "the notice names a cleanup command when the legacy line is the whole file" '[ -n "$cleanup_cmd" ]'
+eval "$cleanup_cmd" || fail "the printed cleanup command failed on an exclude file holding only the legacy line"
+check "the cleanup command removes a legacy line that is the whole file" '! grep -qxF .npmrc "$bcommon/info/exclude"'
+check "the cleanup command leaves no temporary file behind" '[ ! -e "$bcommon/info/exclude.tmp" ]'
+
 # The assertion: an .npmrc git does not ignore makes link fail.
 git -C "$WORK/main" worktree add -q "$WORK/wt2" -b linked2
 # A global excludes file is not what we control, so defeat the ignore by negating it in .gitignore.