ci: Make false-positive patterns match a single warning

Otherwise, it's possible for a pattern to correspond to several
warnings, not all of which are false positives. By adding sufficiently
precise patterns as indicated in the comments, this is unlikely, but not
impossible.

In the case of this pattern, for example, currently present in
xfce4-panel:
tasklist-widget.c:[0-9]+:[0-9]+: warning: dereference of NULL 'child' \[CWE-476\] \[-Wanalyzer-null-dereference\]
the 'child' variable has enough occurrences in the tasklist-widget.c
file that the risk of a multiple match cannot be ruled out.

The simplest way to specify a multiple match seems to be to add the
pattern several times, instead of specifying the number of matches,
which would require additional parsing with a delimiter.

Amends: 8bf2175d

ci/build_project.yml

@@ -192,7 +192,8 @@ release:
   # * if the false positive file doesn't exist or is empty, the build warning list must be empty;
   # * if the file is not empty:
   #   * the build warning list filtered by the file patterns must be empty;
-  #   * each file pattern must match at least one build warning.
+  #   * each file pattern must match exactly one build warning; if a pattern is to match several
+  #     warnings, it must be added as many times.
   # Empty lines and lines starting with '#' in the false positive file are ignored (so you can
   # comment on the addition of a false positive).
   # Patterns added to this file should be as restrictive as possible, so that they normally
@@ -208,12 +209,13 @@ release:
     - '[ -f "$FALSE_POSITIVE_FILE" ] || { echo "$warnings"; exit 1; }'
     - 'filtered_warnings=$(grep -Ev -f <(sed -E "/^#|^$/d" "$FALSE_POSITIVE_FILE") <<< "$warnings" || true)'
     - '[ -z "$filtered_warnings" ] || { echo "$filtered_warnings"; exit 1; }'
-    - 'while read -r false_positive; do
-         grep -Eq "$false_positive" <<< "$warnings" || orphans=("${orphans[@]}" "$false_positive");
-       done < <(sed -E "/^#|^$/d" "$FALSE_POSITIVE_FILE")'
-    - '[ -z "${orphans[*]}" ] || {
-         printf "%s\n"
-           "These patterns no longer match any warning and should be remove from ''"$FALSE_POSITIVE_FILE"'':"
-           "${orphans[@]}";
+    - 'n_warnings=$(wc -l <<< "$warnings")'
+    - 'n_patterns=$(sed -E "/^#|^$/d" "$FALSE_POSITIVE_FILE" | wc -l)'
+    - 'if ((n_warnings < n_patterns)); then
+         echo "Some patterns no longer match any warning and should be remove from ''$FALSE_POSITIVE_FILE''";
          exit 1;
-       }'
+       elif ((n_warnings > n_patterns)); then
+         echo "Some patterns match several warnings, but have either not been added to ''$FALSE_POSITIVE_FILE''
+               enough times, or some of the warnings they match are not false positives";
+         exit 1;
+       fi'