Add backups command.

`backups` provides subcommands for managing backups of the hosts file.

README.md

@@ -46,6 +46,7 @@ A package for Arch users is also [available in the AUR](https://aur.archlinux.or
 Usage:
   hosts [<search string>]
   hosts add <ip> <hostname> [<comment>]
+  hosts backups [create | [compare | delete | restore | show] <filename>]
   hosts block <hostname>...
   hosts disable (<ip> | <hostname> | <search string>)
   hosts disabled
@@ -109,6 +110,31 @@ Description:
   Add a given IP address and hostname pair, along with an optional comment.
 ```
 
+### `hosts backups`
+
+```text
+Usage:
+  hosts backups
+  hosts backups create
+  hosts backups compare <name>
+  hosts backups delete  <name>
+  hosts backups restore <name> --skip-backup
+  hosts backups show    <name>
+
+Subcommands:
+  backups           List available backups.
+  backups create    Create a new backup of the hosts file.
+  backups compare   Compare a backup file with the current hosts file.
+                    The diff tool configured for git will be used if
+                    one is set.
+  backups delete    Delete the specified backup.
+  backups restore   Replace the contents of the hosts file with a
+                    specified backup. The hosts file is automatically
+                    backed up before being overwritten unless the
+                    '--skip-backup' flag is specified.
+  backups show      Show the contents of the specified backup file.
+```
+
 ### `hosts block`
 
 ```text

hosts

@@ -611,6 +611,7 @@ Version: ${_VERSION}
 Usage:
   ${_ME} [<search string>]
   ${_ME} add <ip> <hostname> [<comment>]
+  ${_ME} backups [create | [compare | delete | restore | show] <filename>]
   ${_ME} block <hostname>...
   ${_ME} disable (<ip> | <hostname> | <search string>)
   ${_ME} disabled
@@ -634,8 +635,6 @@ Options:
 
 Help:
   ${_ME} help [<command>]
-
-$(commands)
 HEREDOC
   fi
 }
@@ -750,6 +749,148 @@ add() {
   fi
 }
 
+# --------------------------------------------------------------------- backups
+
+desc "backups" <<HEREDOC
+Usage:
+  ${_ME} backups
+  ${_ME} backups create
+  ${_ME} backups compare <name>
+  ${_ME} backups delete  <name>
+  ${_ME} backups restore <name> --skip-backup
+  ${_ME} backups show    <name>
+
+Subcommands:
+  backups           List available backups.
+  backups create    Create a new backup of the hosts file.
+  backups compare   Compare a backup file with the current hosts file.
+                    The diff tool configured for git will be used if
+                    one is set.
+  backups delete    Delete the specified backup.
+  backups restore   Replace the contents of the hosts file with a
+                    specified backup. The hosts file is automatically
+                    backed up before being overwritten unless the
+                    '--skip-backup' flag is specified.
+  backups show      Show the contents of the specified backup file.
+HEREDOC
+backups() {
+  local _subcommand="${1:-}"
+  shift
+
+  local _hosts_dirname
+  _hosts_dirname="$(dirname "${HOSTS_PATH}")"
+
+  case "${_subcommand}" in
+    create)
+      _verify_write_permissions "$@"
+
+      local _timestamp
+      _timestamp="$(date +"%Y%m%d%H%M%S")"
+
+      cp "${HOSTS_PATH}" "${HOSTS_PATH}--backup-${_timestamp}" && \
+        printf "Backed up to %s--backup-%s\n" "${HOSTS_PATH}" "${_timestamp}"
+      ;;
+    compare)
+      if [[ -z "${1:-}" ]]
+      then
+        "$_ME" help backups
+        exit 1
+      elif [[ ! -e "${_hosts_dirname}/${1}" ]]
+      then
+        printf "Backup not found: %s\n" "${1:-}"
+        exit 1
+      fi
+
+      local _difftool="diff"
+      if command -v git &>/dev/null
+      then
+        _difftool="$(git config --get merge.tool)"
+      fi
+
+      "${_difftool}" "${HOSTS_PATH}" "${_hosts_dirname}/${1}"
+      ;;
+    delete)
+      if [[ -z "${1:-}" ]]
+      then
+        "$_ME" help backups
+        exit 1
+      fi
+
+      _verify_write_permissions "$@"
+
+      if [[ "${HOSTS_PATH}" != "${_hosts_dirname}/${1:-}" ]] &&
+         [[ -e "${_hosts_dirname}/${1:-}" ]]
+      then
+        rm "${_hosts_dirname}/${1:-}" &&
+          printf "Backup deleted: %s\n" "${_hosts_dirname}/${1:-}"
+      else
+        printf "Backup not found: %s\n" "${1:-}"
+        exit 1
+      fi
+      ;;
+    restore)
+      if [[ -z "${1:-}" ]]
+      then
+        "$_ME" help backups
+        exit 1
+      elif [[ ! -e "${_hosts_dirname}/${1}" ]]
+      then
+        printf "Backup not found: %s\n" "${1:-}"
+        exit 1
+      fi
+
+      _verify_write_permissions "$@"
+
+      if [[ "${2:-}" != "--skip-backup" ]]
+      then
+        "${_ME}" backups create
+      fi
+
+      cat "${_hosts_dirname}/${1}" > "${HOSTS_PATH}" &&
+        printf "Restored from backup: %s\n" "${1}"
+      ;;
+    show)
+      if [[ -z "${1:-}" ]]
+      then
+        "$_ME" help backups
+        exit 1
+      elif [[ ! -e "${_hosts_dirname}/${1}" ]]
+      then
+        printf "Backup not found: %s\n" "${1:-}"
+        exit 1
+      fi
+
+      less "${_hosts_dirname}/${1:-}"
+      ;;
+    *)
+      local _filenames=()
+
+      set +f
+      for __filename in $(cd "${_hosts_dirname}" && ls -1 hosts* 2> /dev/null)
+      do
+        if [[ "${__filename:-}" != "hosts" ]] && \
+           [[ ! "${__filename:-}" =~ ^hosts_test..{6}$ ]]
+        then
+          _filenames+=("${__filename:-}")
+        fi
+      done
+      set -f
+
+      if ((${#_filenames[@]}))
+      then
+        for __filename in "${_filenames[@]:-}"
+        do
+          printf "%s\n" "${__filename}"
+        done
+      else
+        printf \
+          "No backups found. Create a new backup:\n %s backups create\n" \
+          "${_ME}"
+      fi
+      ;;
+  esac
+}
+
 # ----------------------------------------------------------------------- block
 
 desc "block" <<HEREDOC

test/backups.bats

@@ -0,0 +1,233 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+# `hosts backups` #############################################################
+
+@test "\`backups\` with no backups and no arguments exits with status 0." {
+  run "${_HOSTS}" backups
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 0 ]]
+}
+
+@test "\`backups\` with backups and no arguments exits with status 0." {
+  {
+    run "${_HOSTS}" backups create
+  }
+
+  run "${_HOSTS}" backups
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 0 ]]
+}
+
+@test "\`backups\` with no backups and no arguments prints message." {
+  run "${_HOSTS}" backups
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  _expected="\
+No backups found. Create a new backup:
+ hosts backups create"
+  [[ "${output}" == "${_expected}" ]]
+}
+
+@test "\`backups\` with backups and no arguments prints list of backups." {
+  {
+    run "${_HOSTS}" backups create
+    sleep 1
+    run "${_HOSTS}" backups create
+  }
+
+  run "${_HOSTS}" backups
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ "${lines[0]}" =~ hosts_test ]]
+  [[ "${lines[0]}" =~ '--backup-' ]]
+  [[ "${lines[1]}" =~ hosts_test ]]
+  [[ "${lines[1]}" =~ '--backup-' ]]
+}
+
+# `hosts backups create` ######################################################
+
+@test "\`backups create\` exits with status 0." {
+  run "${_HOSTS}" backups create
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 0 ]]
+}
+
+@test "\`backups create\` creates backup." {
+  run "${_HOSTS}" backups create
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+  printf "\${_backup_path}: '%s'\\n" "${_backup_path}"
+  [[ -e "${_backup_path}" ]]
+}
+
+@test "\`backups create\` prints message." {
+  run "${_HOSTS}" backups create
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${output} =~ 'Backed up to' ]]
+}
+
+# `hosts backups compare` #####################################################
+
+@test "\`backups compare\` with valid backup exits with status 0 and prints." {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups show "${_backup_basename}"
+  printf "\${output}: '%s'\\n" "${output}"
+  printf "\${lines[6]}: '%s'\\n" "${lines[6]}"
+  [[ ${status} -eq 0 ]]
+  [[ "${lines[6]}" == '127.0.0.1	localhost' ]]
+}
+
+@test "\`backups compare\` with invalid backup exits with status 1" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups compare "invalid-backup-name"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 1 ]]
+  [[ ${output} =~ 'Backup not found' ]]
+}
+
+# `hosts backups delete` ######################################################
+
+@test "\`backups delete\` with valid backup exits with status 0 and deletes backup" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups delete "${_backup_basename}"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 0 ]]
+  [[ ! -e "${_backup_path}" ]]
+  [[ ${output} =~ 'Backup deleted' ]]
+}
+
+@test "\`backups delete\` with invalid backup exits with status 1" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups delete "invalid-backup-name"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 1 ]]
+  [[ -e "${_backup_path}" ]]
+  [[ ${output} =~ 'Backup not found' ]]
+}
+
+# `hosts backups restore` #####################################################
+
+@test "\`backups restore\` with valid backup exits with status 0 and restores" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    sleep 1
+  }
+
+  run "${_HOSTS}" backups restore "${_backup_basename}"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  printf "\${lines[0]}: '%s'\\n" "${lines[0]}"
+  [[ ${status} -eq 0 ]]
+  [[ "${lines[0]}" =~ 'Backed up to' ]]
+  [[ "${lines[1]}" =~ 'Restored from backup' ]]
+
+  _new_backup_path="$(echo "${lines[0]}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+
+  _new_backup_content="$(cat "${_new_backup_path}")"
+  _old_backup_content="$(cat "${_backup_path}")"
+  _current_content="$(cat "${HOSTS_PATH}")"
+
+  [[ "${_new_backup_content}" != "${_current_content}" ]]
+  [[ "${_old_backup_content}" == "${_current_content}" ]]
+}
+
+@test "\`backups restore --skip-backup\` with valid backup exits with status 0 and restores" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+    run "${_HOSTS}" add 0.0.0.0 example.com
+    _replaced_content="$(cat "${HOSTS_PATH}")"
+    sleep 1
+  }
+
+  run "${_HOSTS}" backups restore "${_backup_basename}" --skip-backup
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  printf "\${lines[0]}: '%s'\\n" "${lines[0]}"
+  [[ ${status} -eq 0 ]]
+  [[ "${lines[0]}" =~ 'Restored from backup' ]]
+
+  _old_backup_content="$(cat "${_backup_path}")"
+  _current_content="$(cat "${HOSTS_PATH}")"
+
+  [[ "${_replaced_content}"   != "${_current_content}" ]]
+  [[ "${_old_backup_content}" == "${_current_content}" ]]
+}
+
+@test "\`backups restore\` with invalid backup exits with status 1" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups restore "invalid-backup-name"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 1 ]]
+  [[ ${output} =~ 'Backup not found' ]]
+}
+
+# `hosts backups show` ########################################################
+
+@test "\`backups show\` with valid backup exits with status 0 and prints." {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups show "${_backup_basename}"
+  printf "\${output}: '%s'\\n" "${output}"
+  printf "\${lines[6]}: '%s'\\n" "${lines[6]}"
+  [[ ${status} -eq 0 ]]
+  [[ "${lines[6]}" == '127.0.0.1	localhost' ]]
+}
+
+@test "\`backups show\` with invalid backup exits with status 1" {
+  {
+    run "${_HOSTS}" backups create
+    _backup_path="$(echo "${output}" | sed -e 's/.*\(\/tmp.*\)/\1/')"
+    _backup_basename="$(basename "${_backup_path}")"
+  }
+
+  run "${_HOSTS}" backups show "invalid-backup-name"
+  printf "\${status}: %s\\n" "${status}"
+  printf "\${output}: '%s'\\n" "${output}"
+  [[ ${status} -eq 1 ]]
+  [[ ${output} =~ 'Backup not found' ]]
+}

test/test_helper.bash

@@ -12,8 +12,9 @@ setup() {
   # The location of the `hosts` script being tested.
   export _HOSTS="${BATS_TEST_DIRNAME}/../hosts"
 
+  export _HOSTS_TEMP_DIR="/tmp"
   export _HOSTS_TEMP_PATH
-  _HOSTS_TEMP_PATH="$(mktemp /tmp/hosts_test.XXXXXX)" || exit 1
+  _HOSTS_TEMP_PATH="$(mktemp ${_HOSTS_TEMP_DIR}/hosts_test.XXXXXX)" || exit 1
   cat "${BATS_TEST_DIRNAME}/fixtures/hosts" > "${_HOSTS_TEMP_PATH}"
 
   export HOSTS_PATH="${_HOSTS_TEMP_PATH}"
@@ -24,7 +25,7 @@ teardown() {
      [[ -e "${_HOSTS_TEMP_PATH}" ]] &&
      [[ "${_HOSTS_TEMP_PATH}" =~ ^/tmp/hosts_test ]]
   then
-    rm "${_HOSTS_TEMP_PATH}"
+    rm -f "${_HOSTS_TEMP_DIR}"/hosts_test.*
   fi
 }