How to quickly checkout github pull request

Two ways:

1.
$ git fetch origin pull/117/head:local-branch-name
$ git checkout local-branch-name

Or you can put in  ~/.profile following function:

checkoutPull() {
  #Usage: checkoutPull pr-number pr-branch
  #   or  checkoutPull pr-number user:pr-branch
  BRACH=$(echo $2 | sed -e "s/^.*://")
  if git branch | grep $BRACH; then
    echo "Branch $BRACH already exists and should be removed"
    read -p "Are you sure (y/n)? " -n 1 -r
    echo    # (optional) move to a new line
    if [[ $REPLY =~ ^[Yy]$ ]]
    then
      git branch -D $BRACH
    fi
  fi
  echo "git fetch upstream pull/$1/head:$BRACH"
  git fetch upstream pull/$1/head:$BRACH
  echo "git checkout $BRACH"
  git checkout $BRACH
}

And use it as:
$ checkoutPull 3058 my-coworker-username:issue-51502

2.
One more approach is or create function that consume easy to copy value from Github page. All PRs pages show this value as text "my-coworker-fork:his-branch".
Add to ~/.profile
checkoutForked() {
  #usage: checkoutForked another-fork:branch-in-fork
  FORK=$(echo $1 | cut -d ':' -f 1)
  BRANCH=$(echo $1 | cut -d ':' -f 2)
  REPO=$(grep -A 1 "\"origin\"" .git/config | grep github | sed -E "s/.*\///");
  if git remote | grep $FORK; then
    echo "Fork already exists"
  else
    echo "git remote add $FORK git@github.com:$FORK/$REPO;"
    git remote add $FORK git@github.com:$FORK/$REPO;
  fi
  echo "git fetch $FORK"
  git fetch $FORK
  if git branch | grep $FORK/$BRANCH; then
    echo "Branch $FORK/$BRANCH already exists"
  else
    echo "git checkout $FORK/$BRANCH"
    git checkout $FORK/$BRANCH
    echo "git checkout -b $FORK/$BRANCH"
    git checkout -b $FORK/$BRANCH
  fi
}
execute:
$ checkoutForked my-coworker-fork:his-branch

NOTE:
to push to forked repo remote you will need bind your branch and his branch:
git push my-coworker-fork my-coworker-fork/his-branch:his-branch -f

How to find and install missed man page or section in linux

Two options:
1) web
2) in server repositories

1) In web - just google it
https://www.google.com/search?q=man+7+signal
Will result in smth like http://man7.org/linux/man-pages/man7/signal.7.html

2) In server
$ man kill
# no signals details , most likely in "SEE ALSO .... signals(7)"

$ man 7 signal
No manual entry for signal in section 7

$ yum provides */signal.7.gz
...
#man-pages-3.53-5.el7.noarch : Man (manual) pages from the Linux Documentation Project
#Repo : rhel-7-server-rpms-master
#Matched from:
#Filename : /usr/share/man/man7/signal.7.gz
..

$ sudo yum install man-pages

$ man 7 signal