ELEC-175: Added SchLib diff tool (#12)

Added tool for diffing Schematic Diagrams.SchLib. Displays the difference between two given branches.

diff_schlib.sh

@@ -0,0 +1,41 @@
+#!/bin/bash
+
+# Usage: ./diff_schlib.sh branch_a branch_b
+#
+# Example: ./diff_schlib.sh master elec_135_elec_161_chaos
+#
+# Also supports specific commits!
+#
+# Example: ./diff_schlib.sh 1fef master
+
+pip3 install olefile > /dev/null
+
+read_schlib() {
+  filename="Schematic Diagrams.SchLib"
+
+  arg=$(git ls-remote --heads https://github.com/uw-midsun/hardware.git | grep -om1 "${1}.*")
+  if [ -z "${arg}" ]; then
+    arg=$(git rev-parse --verify "${1}^{commit}")
+    if [ $? -ne 0 ]; then
+      exit 1
+    fi
+  fi
+
+  wget -q "https://raw.githubusercontent.com/uw-midsun/hardware/${arg}/altium-lib/${filename}" -O "${arg}.SchLib"
+  python3 -c "import olefile; [print(x[0]) for x in olefile.OleFileIO('${arg}.SchLib').listdir(streams=False, storages=True)]" | sort
+
+  rm -f "${arg}.SchLib"
+}
+
+YELLOW=$(tput bold && tput setaf 3)
+GREEN=$(tput bold && tput setaf 2)
+RED=$(tput bold && tput setaf 1)
+CLEAR=$(tput sgr0)
+
+NEW='\+'
+DEL='\-'
+
+lib_diff="${1}! !${2}\n"
+lib_diff+=$(comm -3 --output-delimiter='!' <(read_schlib "${1}" | sort) <(read_schlib "${2}" | sort) | sed -r "s/!/ !${NEW}!/; s/^([^ ].*)$/\1!${DEL}!/")
+
+echo -e "${lib_diff}" | column -s '!' -t | sed -r "s/^${1}([[:space:]]+)${2}$/${YELLOW}${1}\1${2}${CLEAR}/; s/ ${DEL}/ ${RED}${DEL}${CLEAR}/; s/ ${NEW}/ ${GREEN}${NEW}${CLEAR}/"