Git Notes

One-liners

• Diff commits: git diff <old hash>^..<new hash>
• Tag a commit: git tag <tag name> <commit hash>
• List tags: git tag -l

Add files to an old commit

• Save changes using git stash
• Use git rebase -i HEAD~10 (or however many commits back you want to see)
• Mark the commit in question for edit by changing the word pick at the start of the line into edit. Do not delete the other lines as that would delete the commits
• Save the rebase file, and git will drop back to the shell and wait for you to fix that commit
• Pop the stash: git stash pop
• Add file(s) with git add <files>
• Amend the commit with git commit --amend --no-edit
• Do git rebase --continue which will rewrite the rest of your commits against the new one

Edit an old commit

• Commit needed changes
• Save unneeded changes using git stash
• Use git rebase -i HEAD~10 (or however many commits back you want to see)
• Move the newest commit (your fix) to the line below the old commit you want to edit
• Squash this new commit by changing the word pick at the start of the line into squash. Do not delete the other lines as that would delete the commits
• Save the rebase file, and git will drop you into an editor where you can edit the updated commit message
• Fix any merge conflicts and run git rebase --continue

Rebase master onto a branch

$ git checkout master
$ git pull origin master
$ git rebase master <branch>
# Make manual changes as needed
$ git rebase --continue

Pushing a rebased branch to a remote will require --force:

$ git push origin <branch> --force

Extract part of a repo to a new repo

IMPORTANT: Start with a fresh clone of the repository, not your working copy

• Remove origin, just in case: git remote rm origin
• Filter out what you want to keep: git filter-branch --subdirectory-filter <directory> -- --all
• Clean unwanted data:

$ git reset --hard
$ git gc --aggressive
$ git prune
$ git clean -fd

Convert Remote CVS Repository to Git

• Install necessary packages: dnf install git-cvs rsh
• Import CVS repository

$ git cvsimport -v -d <CVS repo path> <module>
# where CVS repo path is similar to
#    :pserver:anonymous@a.cvs.sourceforge.net:/cvsroot/pcal

Applying patches with git

$ git apply --reject --whitespace=fix <patch>
$ wiggle --replace <file> <file.rej>

Diff

• export GIT_PAGER=vim -c "runtime! macros/less.vim" -
• use –no-color for git diff

Send patches by email

# Install and configure git-email
$ sudo dnf install git-email
$ git config --global user.name "My name"
$ git config --global user.email me@mail.com

# See https://git-send-email.io/
# and https://www.futurile.net/2022/03/07/git-patches-email-workflow/
[sendemail]
    smtpserver = smtp.gmail.com
    smtpencryption = ssl
    smtpserverport = 465
    smtpuser = jbru362@gmail.com
    smtpPass = !pass gmail/oauth

# Create the patch and send it
$ git format-patch -N # where N is the number of commits from HEAD to include
$ git send-email \
    --to maintainer@mail.com \
    --smtp-pass $(pass gmail/oauth | head -1) \
    <file.patch>
# Use the --annotation switch to edit the email
# Use the --dry-run switch to test