git-diff-branch

#!/usr/bin/env bash
set -euo pipefail

if [[ $# == 0 ]]; then
    echo "Usage:" >&2
    echo "  git diff-branch [-m] BRANCH [GIT_DIFF_ARGUMENTS]" >&2
    exit 1
fi

MATCH=$1
shift

MAJOR=N
if [[ "$MATCH" == "-m" ]]; then
    MAJOR=Y
    MATCH=$1
    shift
fi;

: "${REMOTE:=origin}"
REMOTE_URL=$(git remote get-url "$REMOTE")
if [[ "${REMOTE_URL%/*}" != "git@github.com:odoo" ]]; then
    echo "🚫 This tool only works on github.com/odoo repositories. URL of remote ${REMOTE} is '${REMOTE_URL}'." >&2
    exit 1
fi

AWK="awk"
if command -v gawk >/dev/null; then
    AWK="gawk"
fi

PREV=$(
    # shellcheck disable=SC2016
    git branch --remotes --list "${REMOTE}"'/*' | $AWK -F/ '!/tmp|staging|nightly|HEAD/ {
        branch=$2;
        len = split(gensub("saas-", "", 1, branch), a, ".");
        if(len == 1) {
            a[2] = a[1];
            switch(a[2]) {
                case "master":
                    a[1] = a[2] = 9999;
                    break;
                case /^[1-5]$/:
                    a[1] = 7;
                    break;
                case 6:
                    a[1] = 8;
                    break;
                case /^[789]$|^1[0123]$/:
                    a[1] = 9;
                    break;
                case /^1[45678]$/:
                    a[1] = 10;
                    break;
                default:
                    a[1] = -1;
            };
        }
        else if (len != 2 || int(a[1]) < 1 || int(a[2]) != a[2])
            a[1] = -1;

        if (a[1] != -1)
            printf("%d.%02d:%s\n", a[1], a[2], branch);
    }' | sort -n | $AWK -F: --assign "MATCH=$MATCH" --assign "MAJOR=$MAJOR" '{
        branch = $2;
        if (branch == MATCH) {
            print prev
        }
    }
    {
        if (MAJOR == "N" || index($1, ".00") != 0) {
            prev = branch;
        };
    }'
)

if [[ -z "$PREV" ]]; then
    echo "🙁 Cannot determine previous branch of $MATCH" >&2
    exit 1
fi

set -x
git diff --no-prefix "${REMOTE}/${PREV}..${REMOTE}/${MATCH}" "$@"