[PATCH 3/2] init: support git <2.30 for "-c KEY=VALUE" args

[Eric Wong <e@80x24.org>]

It turns out `--fixed-value' is a relatively new git-config(1)
feature in git 2.30+ (December 2020).  So use the quotemeta
perlop for now since it seems compatible-enough for POSIX ERE
used by git.
---
 script/public-inbox-init | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/script/public-inbox-init b/script/public-inbox-init
index e22a0564..6fac4d18 100755
--- a/script/public-inbox-init
+++ b/script/public-inbox-init
@@ -231,8 +231,11 @@ run_die([@x, "$pfx.newsgroup", $ng]) if $ng ne '';
 
 for my $kv (@c_extra) {
 	my ($k, $v) = split(/=/, $kv, 2);
-	# --fixed-value for idempotent invocations
-	run_die([@x, qw(--replace-all --fixed-value), "$pfx.$k", $v, $v]);
+	# git 2.30+ has --fixed-value for idempotent invocations,
+	# but that's too new to depend on in 2021.  Perl quotemeta
+	# seems compatible enough for POSIX ERE which git uses
+	my $re = '^'.quotemeta($v).'$';
+	run_die([@x, qw(--replace-all), "$pfx.$k", $v, $re]);
 }
 
 # needed for git prior to v2.1.0