Git misc Tips

How to checkout a specific version of one file?

 

git checkout <commit hash> <filepath in this commit>

git checkout <commit hash> -- checkout all files in this commit

 

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How to diff two versions of one file?

 

git diff HEAD^ HEAD <filepath>

git diff <start commit hash>..<end commit hash> <filepath>

 

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Merge CAUTION:

 

When merge one branch to another(E.g: merge branch A to branch master), git will ONLY CARE the conflict on one line. If both branch modified the same line, conflict occurs(default merge strategy). So, if branch A DELETED some lines in a file while these lines does exist in branch master, there will NO CONFLICT reported. The merged version is the version in branch A.

 

So, if one file will be modified by 2 guys. We should create 2 branches for these 2 guys. When they finished modifying, commit changes then use "git merge trunk b1 b2" to merge these 2 branches into trunk branch. This will combine all changes into trunk. We CAN'T apply 1 guy's change to trunk, then create another branch for another guy, finally merge new branch into trunk. This will cause problems just described above.

 

And, merge is not always correct. More times merge will fail, especially when we merge a lot of branches together. So, be careful for the output when "git merge". If output message shows failed which git tried all merge methods, we can't take this merge result. We should delete this branch and create new branch for merging again. This time try to merge less branches, no conflict branches together. The goal is to make "git merge" no error occurs. Conflict is correct and we can take care of it but merge can't failed.

 

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Commit will NOT auto add new files

 

git commit -a will NOT call git-add to add new files. git commit -a just commit modified files. So if have new files added, please use git add first, then git commit -a.

 

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How to check one file's log and How to show the affected files in one commit

 

git log <filepath> -- check this file's log separately

git log --name-only -- show affected files in every commit

 

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How to rename and remove files

 

git mv <file original name> <file new name>

git rm <file path>

git rm -r <dir path> -- remove a directory

 

All these should be use "git commit" next to make changes effect.

 

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How to modify commit message?

 

1. If you wanna modify the latest commit's message, just:

   git commit --amend -m "new message here..."

2. If you wanna modify NOT the latest commit's message, just:

   git rebase -i HEAD~5 -- list 5 commit in editor, then change the "pick" to "edit" in the commit line which you wanna modify

   git commit --amend -m "new message"

   git rebase --continue