Classifying a branch as master or dev
Personally, I see no problem doing it either way. I prefer to keep my lines shorter than that but 120ish characters isn't unreasonable.

Another option you have is to store those values in some other variables and use those instead.

let isMaster = branchInfo.name === BRANCHNAMES.MASTER;
let isRelease = branchInfo.name === BRANCHNAMES.RELEASE;
let isHotfix = branchInfo.name === BRANCHNAMES.HOTFIX;
if (isMaster) {
    branchInfo.isMaster = true;
} else if (isRelease || isHotfix) {
    branchInfo.isDev = true;
}


Another way would be to use a switch statement with case fallthrough. Some people refuse to allow fallthrough so it's your call.

switch (branchInfo.name) {
    case BRANCHNAMES.MASTER:
        branchInfo.isMaster = true;
        break;

    case BRANCHNAMES.RELEASE:
    case BRANCHNAMES.HOTFIX:
        branchInfo.isDev = true;
}


Finally, I would consider just assigning directly.

branchInfo.isMaster = branchInfo.name === BRANCHNAMES.MASTER;
branchInfo.isDev = branchInfo.name === BRANCHNAMES.RELEASE ||
                   branchInfo.name === BRANCHNAMES.HOTFIX;


There's also one trick I use if I need to compare against multiple things at once.

let devBranches = [BRANCHNAMES.RELEASE, BRANCHNAMES.HOTFIX];
branchInfo.isMaster = branchInfo.name === BRANCHNAMES.MASTER;
branchInfo.isDev = devBranches.includes(branchInfo.name);


If you don't perform any extra work in either branch of the if statement, I would use the last or second to last option. If you need to perform additional work, I would use the additional variables to make it more readable.