[PATCH proxmox-acme 2/3] acme: add missing _url_replace function

[Mathias Bartmann <mathias.bartmann@gmail.com>]

dns_yc.sh (Yandex Cloud) pipes the header and payload of the JWT it
signs through _url_replace to turn base64 into base64url, but the
proxmox-acme shim does not define that helper. Add it as in upstream
acme.sh.

Signed-off-by: Mathias Bartmann <mathias.bartmann@gmail.com>
---
 src/proxmox-acme           | 4 ++++
 src/test/test-shim-helpers | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/src/proxmox-acme b/src/proxmox-acme
index 00f4c06..7d776ce 100644
--- a/src/proxmox-acme
+++ b/src/proxmox-acme
@@ -28,6 +28,10 @@ _mktemp() {
   mktemp
 }
 
+_url_replace() {
+  tr '/+' '_-' | tr -d '= '
+}
+
 # Usage: hashalg  [outputhex]
 # Output Base64-encoded digest
 _digest() {
diff --git a/src/test/test-shim-helpers b/src/test/test-shim-helpers
index b625a53..d4ec5a3 100755
--- a/src/test/test-shim-helpers
+++ b/src/test/test-shim-helpers
@@ -30,5 +30,8 @@ else
     fail "_mktemp does not create a writable temporary file"
 fi
 
+[ "$(printf '%s' 'ab/c+d==' | $SHIM _url_replace)" = 'ab_c-d' ] ||
+    fail "_url_replace does not convert base64 to base64url"
+
 [ "$FAILED" -eq 0 ] || exit 1
 echo "OK: proxmox-acme helpers behave like upstream acme.sh."
-- 
2.55.0