cocci: matching (multiple) identifiers

"make coccicheck" seems to work OK at GitHub CI using

    $ spatch --version
    spatch version 1.1.1 compiled with OCaml version 4.13.1
    OCaml scripting support: yes
    Python scripting support: yes
    Syntax of regular expressions: PCRE

but not with

    $ spatch --version
    spatch version 1.3 compiled with OCaml version 5.3.0
    OCaml scripting support: yes
    Python scripting support: yes
    Syntax of regular expressions: Str

Judging from https://ocaml.org/manual/5.3/api/Str.html, I suspect
that this probably is caused by the distinction between BRE vs PCRE.
As there is no reasonably clean way to write the multiple choice
matches portably between these two pattern languages, let's stop
using regexp_constraint and use compare_constraint instead when
listing the function names to exclude.

There are other uses of "!~" but they all want to match a single
simple token, that should work fine either with BRE or PCRE.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/coccinelle/commit.cocci

diff --git a/contrib/coccinelle/commit.cocci b/contrib/coccinelle/commit.cocci
index af6dd4c..c528460 100644
--- a/contrib/coccinelle/commit.cocci
+++ b/contrib/coccinelle/commit.cocci
@@ -25,7 +25,8 @@
 // functions, then the recommended transformation will be bogus with
 // repo_get_commit_tree() on the LHS.
 @@
-identifier f !~ "^(repo_get_commit_tree|get_commit_tree_in_graph_one|load_tree_for_commit|set_commit_tree)$";
+identifier f != { repo_get_commit_tree, get_commit_tree_in_graph_one,
+		  load_tree_for_commit, set_commit_tree };
 expression c;
 @@
   f(...) {<...