プロジェクトを新規に作成するときに、gitignoreの中身を作るのがちょっと面倒。
そんなときは、gemignoreを使うと良さそう。github/gitignoreに保存されている様々なgitignoreを取り込むことができます。

インストール方法

gemでインストールします。gemのインストールはネットでいっぱいあるので調べてみてください。

$ gem install gemignore

使い方

例：swiftプロジェクトの場合

$ cd xcodeのプロジェクトルート
$ touch .gitignore
$ gemignore add swift

これで.gitignoreがこんな感じになります。

.gitignore

# Added by gemignore. Snippet 'Swift'
# Xcode
#
# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore

## Build generated
build/
DerivedData

## Various settings
*.pbxuser
!default.pbxuser
*.mode1v3
!default.mode1v3
*.mode2v3
!default.mode2v3
*.perspectivev3
!default.perspectivev3
xcuserdata

## Other
*.xccheckout
*.moved-aside
*.xcuserstate
*.xcscmblueprint

## Obj-C/Swift specific
*.hmap
*.ipa

# CocoaPods
#
# We recommend against adding the Pods directory to your .gitignore. However
# you should judge for yourself, the pros and cons are mentioned at:
# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
#
# Pods/

# Carthage
#
# Add this line if you want to avoid checking in source code from Carthage dependencies.
# Carthage/Checkouts

Carthage/Build

# fastlane
#
# It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
# screenshots whenever they are needed.
# For more information about the recommended setup visit:
# https://github.com/fastlane/fastlane/blob/master/docs/Gitignore.md

fastlane/report.xml
fastlane/screenshots