sort sections

[SolaWing]

as #17, I rewrote sort to support sorting sections. This will ease the pain of Xcode reordering sections and causing huge modifications.

[truebit]

@SolaWing hi, sorry for the late reply.
Thanks for your PR.
As this one is a major change, have you tested on any project file?
I think the quick and lazy verification test is to find some complicated project files being xuniqued twice, to see if they were the same without any error exit.

[ZSaberLv0]

not fully tested, but this PR did solve section sorting problem for my case, without any other side effect @truebit

[SolaWing]

After the first PR, I also fixed some found problem.
The final commit has been used in our team 1 year without any problem.

Maybe we should add auto test?

following is our team's precommithook:

IFS=$'\n' projs=($(git diff --name-only --cached --diff-filter=ACM | grep -o '[a-zA-Z0-9_./]\+\.xcodeproj/project.pbxproj'))
if ((${#projs[@]} > 0)); then
    if command -v python3 >/dev/null 2>&1; then
        py='python3'
    else
        py='python'
    fi
    # set -x
    for proj in ${projs[@]}; do
        $py xUnique.py -c "$proj";
        ret=$?
        if (($ret == 100)); then
            git add "$proj"
        elif (($ret > 0)); then
            echo 'xcodeproj file may broken! check the exception message please'
            echo 'you may add `--no-verify` option for commit to skip checking xcodeproj'
            exit 1
        fi
    done
    if [[ ! $(git diff --name-only --cached | grep -o '[a-zA-Z0-9_./]\+\.xcodeproj/project.pbxproj') ]]; then
        echo 'no changes, commit abort'
        exit 1
    fi
fi

[truebit]

@SolaWing Thanks for the input.
auto test is not a very good alternative, as special project files causing problems are normally from private code, those files cannot be included as a testcase 😟