1. 開啟終端cd到本地倉庫，和.git同層（檢視隱藏檔案）

$ cd project
$ ls -a
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2. 建立.gitignore檔案

$ vim .gitignore
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3. 鍵入 "i"，看到下面這個，進入編輯模式

-- INSERT --
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4. 把下面的這些複製進去

# 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/
*.xcuserstate

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

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

# 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/
#
# Add this line if you want to avoid checking in source code from the Xcode workspace
 

# *.xcworkspace

# 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://docs.fastlane.tools/best-practices/source-control/#source-control

fastlane/report.xml
fastlane/Preview.html
fastlane/screenshots/**/*.png
fastlane/test_output

# Code Injection
#
# After new code Injection tools there's a generated folder /iOSInjectionProject
# https://github.com/johnno1962/injectionforxcode

iOSInjectionProject/
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5. 鍵入 "esc" ，退出編輯模式
6. 鍵入 ":wq" ，儲存並退出

到這裡，就建立好了".gitignore"檔案了！！

建立完以後發現未生效，因為.gitignore只能忽略那些原來沒有被追蹤的檔案，如果某些檔案已經被納入了版本管理中，則修改.gitignore是無效的

7. gitignore規則不生效的解決辦法，先把本地快取刪除然後更新

git rm -r --cached .
git add .
git commit -m 'update .gitignore'
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