Handle signed-by option in __apt_source

Allow users to specify a GPG key fingerprint or keyring file to be
included as the 'signed-by' option.

cdist/conf/type/__apt_source/files/source.list.template

@@ -2,13 +2,14 @@
 set -u
 
 entry="$uri $distribution $component"
+
 cat << DONE
 # Created by cdist ${__type##*/}
 # Do not change. Changes will be overwritten.
 #
 
 # $name
-deb ${forcedarch} $entry
+deb ${options} $entry
 DONE
 if [ -f "$__object/parameter/include-src" ]; then
    echo "deb-src $entry"

cdist/conf/type/__apt_source/man.rst

@@ -23,6 +23,9 @@ OPTIONAL PARAMETERS
 arch
    set this if you need to force and specific arch (ubuntu specific)
 
+signed-by
+   provide a GPG key fingerprint or keyring path for signature checks
+
 state
    'present' or 'absent', defaults to 'present'
 
@@ -56,6 +59,11 @@ EXAMPLES
        --uri http://archive.canonical.com/ \
        --component partner --state present
 
+    __apt_source goaccess \
+       --uri http://deb.goaccess.io/ \
+       --component main \
+       --signed-by C03B48887D5E56B046715D3297BD1A0133449C3D
+   
 
 AUTHORS
 -------

cdist/conf/type/__apt_source/manifest

@@ -31,9 +31,15 @@ fi
 component="$(cat "$__object/parameter/component")"
 
 if [ -f "$__object/parameter/arch" ]; then
-   forcedarch="[arch=$(cat "$__object/parameter/arch")]"
-else
-   forcedarch=""
+   options="arch=$(cat "$__object/parameter/arch")"
+fi
+
+if [ -f "$__object/parameter/signed-by" ]; then
+   options="$options signed-by=$(cat "$__object/parameter/signed-by")"
+fi
+
+if [ "$options" != "" ]; then
+    options="[$options]"
 fi
 
 # export variables for use in template
@@ -41,7 +47,7 @@ export name
 export uri
 export distribution
 export component
-export forcedarch
+export options
 
 # generate file from template
 mkdir "$__object/files"

cdist/conf/type/__apt_source/parameter/optional

@@ -1,4 +1,5 @@
 state
 distribution
 component
-arch
+arch
+signed-by