snap-packaging for gitea (#2568)

* Modify tbraeutigam/gogs-snap for gitea

* Fix building on 16.04 (manually build go-bindata).
-> add _source.tar.bz2 to .gitignore (used by snapcraft cleanbuild)

* Streamline Snap packaging:
 - Take advantage of install-hooks (snapd 2.27)
 - Use snapctl configuration storage for unchanging values

* Move to using Snap Hooks for configuration

* Missed re-adding daemon statement

* Fix two warnings from Codacy.

snap/helpers/configuration.sh

@@ -0,0 +1,126 @@
+#!/bin/bash
+if snapctl get gitea.snap.custom; then
+  cdir=$(snapctl get gitea.snap.custom)
+else
+  cdir=$SNAP_COMMON
+fi
+
+cfg="$cdir/conf/app.ini"
+bak="$cdir/conf/app.ini.bak-$(date -Ins)"
+basecfg="$SNAP/snap/helpers/app.ini"
+smp="$SNAP/gitea/custom/conf/app.ini.sample"
+
+function toSnap() {
+OIFS=$IFS
+IFS='
+'
+  category="none"
+  src="$cfg"
+  [[ "$1" = "init" ]] && src="$smp"
+  [[ "$1" = "snap" ]] && src="$basecfg"
+
+  for l in $(sed 's_;\([A-Z]*\)_\1_g' $src | grep -v -e '^;' -e '^$'); do
+    if echo $l | grep -q '^[[]'; then
+      category=$(CatToSnap "$l")
+    elif echo $l | grep -q '^[A-Z]'; then
+      option=$(OptToSnap "$l")
+      value=$(ValToSnap "$l")
+      if [[ $category = "none" ]]; then
+        snapctl set "$option=$value"
+      else
+        snapctl set "$category.$option=$value"
+      fi
+    fi
+  done
+IFS=$OIFS
+}
+
+function toIni() {
+OIFS=$IFS
+IFS='
+'
+  category="none"; option="none"; catUnset=true
+  src=$smp
+  [[ -f $cfg ]] && src="$cfg"
+  tmpIni="$cfg.tmp"
+  [[ -f $src ]] && cp "$src" "$tmpIni"
+  cp $tmpIni $bak
+  echo '' > $cfg
+  for l in $(grep -v -e '^;' -e '^$' $tmpIni); do
+    if echo $l | grep -q '^[[]'; then
+      category=$(CatToSnap "$l")
+      catUnset=true
+    elif echo $l | grep -q '^[A-Z]'; then
+      option=$(OptToSnap "$l")
+      if [[ $category = "none" ]]; then
+        value=$(snapctl get $option)
+        echo $(OptToIni "$option") = $value >> $cfg
+      else
+        value=$(snapctl get $category.$option)
+        if $catUnset; then
+          echo "" >> $cfg
+          echo "[$(CatToIni "$category")]" >> $cfg
+          catUnset=false
+        fi
+        echo $(OptToIni "$option") = $value >> $cfg
+      fi
+    fi
+  done;
+  IFS=$OIFS
+}
+
+function CatToSnap {
+  ret=$(echo "$1"                             \
+         | grep -oP '[A-Za-z0-9._]+'          \
+         | sed 's|\.|-|g'                     \
+         | sed 's|_|99|g')
+  echo $ret
+}
+function OptToSnap {
+  ret=$(echo "$1"                             \
+         | grep -oP '^[A-Z_]+'                \
+         | tr '[:upper:]' '[:lower:]'         \
+         | sed 's|_|-|g')
+  echo $ret
+}
+function ValToSnap {
+  ret=$(echo "$1"                             \
+         | grep -oP '=.*$'                    \
+         | sed 's_^= __g'                     \
+         | sed 's_^=__g'                      \
+         | sed "s|SNAP_DIR_DATA|$SDATA|g"     \
+         | sed "s|SNAP_DIR_COMMON|$SCOMMON|g" \
+         | sed 's|{}||g')
+  echo $ret
+}
+
+function CatToIni {
+  ret=$(echo "$1"                             \
+         | sed 's|-|.|g'                      \
+         | sed 's|\ |_|g'                     \
+         | sed 's|99|_|g')
+  echo $ret
+}
+function OptToIni {
+  ret=$(echo "$1"                             \
+         | tr '[:lower:]' '[:upper:]'         \
+         | sed 's|-|_|g')
+  echo $ret
+}
+
+[[ "$1" = "configure" ]]             \
+  && toIni                           \
+  && exit 0
+
+[[ "$1" = "install" ]]               \
+  && echo "Initial Configuration..." \
+  && mkdir -p $SNAP_COMMON/conf      \
+  && toSnap init                     \
+  && toSnap snap                     \
+  && toIni sample                    \
+  && exit 0
+
+[[ "$1" = "save" ]]                  \
+  && echo "Saving current config..." \
+  && toSnap                          \
+  && exit 0