Update .ssh/config with "UseKeychain yes" (needed on macOS sierra)

macos-ssh-use-keychain.sh

#!/usr/bin/env bash

# macOS sierra needs an UseKeychain yes SSH config entry in order to use the
# Keychain to store key passphrases. This scripts checks your .ssh/config for
# the existence of such a config entry and prepends the following entry if
# nothing is found:
#
# Host *
#     UseKeychain yes

# fail on errors
set -e
set -u

TARGET=$HOME/.ssh/config
EXISTING=0

# check if target contains UseKeychain config
function checkContent()
{
    grep -q "UseKeychain yes" $TARGET
}

if [ -f $TARGET ]
then
    echo "$TARGET already exists..."
    EXISTING=1

    # check if UseKeychain is already set and abort if so
    if checkContent
    then
        (>&2 echo "ERROR: UseKeychain is already set in $TARGET, please check manually...")
        exit 1
    fi

    BACKUPTARGET=$TARGET-usekeychain-`date +"%Y-%m-%dT%H-%M-%SZ"`.bak
    echo "Backing up $TARGET to $BACKUPTARGET..."
    cp $TARGET $BACKUPTARGET
else
    echo "Creating $TARGET"
    touch $TARGET
fi

# prepend keychain config to SSH config file
if [[ $EXISTING -eq 1 ]]; then
    echo -e "Host *\n   UseKeychain yes\n\n$(cat $TARGET)" > $TARGET
else
    echo -e "Host *\n   UseKeychain yes\n$(cat $TARGET)" > $TARGET
fi

# check results
if checkContent
then
    echo "Successfully updated $TARGET with UseKeychain config"
    exit 0
else
    (>&2 echo "ERROR: Tried to update $TARGET with UseKeychain config, but something went wrong")
    exit 2
fi

curl -s https://gist.githubusercontent.com/maff/e34fc6f6d629d7c4e097c374945a7ab2/raw/61f422905a82306b955ef7f45a9570039c439eb9/macos-ssh-use-keychain.sh | bash

curl -sL https://git.io/vMqal | bash