Tips about Git and Github

Git
Github
Author

Jihong Zhang

Published

March 10, 2024

Scenario: My local changes are ahead of the remote but I want to discard those changes.

This happens when I want to pull the remote repo to local but I have some random changes at local. Those random changes should be discarded but using git pull makes those changes ahead. Thus, I have to restore to previous commit to align with previous commit.

In following code, I type git reset and tab key which will list all recent commits. f17c6d9 is the commit I’m gonna go.

  • git reset f17c6d9 can reset HEAD to the target comit in history, which make local changes as unstaged changes

  • To discard unstaged changes, use git restore .

➜  website-jihong git:(main) git reset            
FETCH_HEAD     HEAD           ORIG_HEAD      main           office         origin/main    origin/office
d636b58  -- [HEAD]    add lecture08 (7 minutes ago)
66dde99  -- [HEAD^]   add lecture08 (9 minutes ago)
f17c6d9  -- [HEAD^^]  adjust sidebar to include previous posts (66 minutes ago)
1211a8e  -- [HEAD~3]  add one new note (14 hours ago)
e4e27b7  -- [HEAD~4]  revide sidebar to include lec08 in quarto.yml (2 days ago)
e479890  -- [HEAD~5]  finish lecture08 (2 days ago)
5f19afd  -- [HEAD~6]  add updates to lecture 08 (2 days ago)
5b90ec6  -- [HEAD~7]  Merge remote-tracking branch 'origin/main' (3 days ago)
d7a9508  -- [HEAD~8]  local changes (3 days ago)
fb69016  -- [fb69016] update lecture08 (4 days ago)
c4f4e29  -- [HEAD~9]  add .rdb in .gitignore (6 days ago)
8feff97  -- [HEAD~10] revise BGGM note (6 days ago)
8b98ac9  -- [HEAD~11] add note of BGGM (6 days ago)
119c64d  -- [HEAD~12] add video link for lecture 4 and 7 (6 days ago)
8417f4a  -- [HEAD~13] revise Lecture07.qmd (7 days ago)
1537f56  -- [HEAD~14] add lecture07 slide11 (7 days ago)
b0bd066  -- [HEAD~15] add keymap doc for iTerm2 (7 days ago)
ff6c8c7  -- [HEAD~16] change color bg and left border (8 days ago)
af18b92  -- [HEAD~17] adjust link and other elements bg-color (8 days ago)
3370b97  -- [HEAD~18] revert back to original giscus setting (8 days ago)
➜  website-jihong git:(main) git reset f17c6d9
Unstaged changes after reset:
M       posts/2024-01-12-syllabus-adv-multivariate-esrm-6553/Lecture08/Lecture08.qmd
➜  website-jihong git:(main) ✗ git restore .    
➜  website-jihong git:(main)

For the future pull while ignore local changes, see this stackoverflow post. There are two methods:

  • Method I:

    • This even works when local changes have already been staged and comitted.
## (1) First fetch all changes:
$ git fetch --all
## (2) Then reset the main:
$ git reset --hard origin/main
## (3) Pull/update:
$ git pull

  • Method II:

    • Use this when you feel like your local changes still useful and DO NOT want to throw them away. This keeps the local changes hidden, but after pulling the remote to local, you pop local changes up afterwards.
$ git stash
$ git pull
$ git stash pop

Scenario: I change the local files after I’ve already git commit

I committed the changes but I change my mind and revise more files. In this case, I do not want to duplicate the commit then complicates my commit history. In this case, I can use --amend to append the new changes to the local changes committed without changing the message.

$ git add the_left_out_file
# The --no-edit flag allows to make an amendment to the commit without changing the commit message.
$ git commit --amend --no-edit
Warning

You should never amend public commits that you already pushed to a public repository, because amend is actually removing the last commit from the history and creating a new commit with the combined changes from that commit and new added when amending.

Previous code works only when I did not push changes yet, if I already pushed, I can do reset.

➜  website-jihong git:(main) git reset f17c6d9
FETCH_HEAD     HEAD           ORIG_HEAD      main           office         origin/main    origin/office
3605a71  -- [HEAD]    add tips about git note (7 minutes ago)
12ceecd  -- [HEAD^]   add tips about git note (8 minutes ago)
f17c6d9  -- [HEAD^^]  adjust sidebar to include previous posts (2 hours ago)
...
3370b97  -- [HEAD~18] revert back to original giscus setting (8 days ago)
➜  website-jihong git:(main) ✗ git reset 12ceecd       
Unstaged changes after reset:
M       notes/2024-03-11-Git-How-To-Use/index.qmd
D       notes/2024-03-11-Git-How-To-Use/index.quarto_ipynb
➜  website-jihong git:(main) ✗ git add .

Because your local commits are different from the remote, note that you should add -f argument to force the remote discards the conflicts.

➜  website-jihong git:(main) git push                                          
To github.com:JihongZ/website-jihong.git
 ! [rejected]        main -> main (non-fast-forward)
error: failed to push some refs to 'github.com:JihongZ/website-jihong.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes (e.g.
hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
➜  website-jihong git:(main) git push -f origin main                                             
Enumerating objects: 13, done.
Counting objects: 100% (13/13), done.
Delta compression using up to 12 threads
Compressing objects: 100% (6/6), done.
Writing objects: 100% (7/7), 1.22 KiB | 1.22 MiB/s, done.
Total 7 (delta 4), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (4/4), completed with 4 local objects.
To github.com:JihongZ/website-jihong.git
 + 3605a71...07ff463 main -> main (forced update)
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