Rebase

rebase interactive

source https://www.atlassian.com/git/tutorials/rewriting-history#git-rebase-i

quote from https://www.atlassian.com/git/tutorials/rewriting-history#git-rebase-i

This gives you the opportunity to alter individual commits in the process, rather than moving all commits.

Tip

$ git fetch –all
$ git rebase -i origin/master --autostash

Rebase interactive in action (basic)

What we get after git rebase -i master:

git-rebase-todo

    pick 3648b69 Meaningful message
    pick 929dbs2 Fix typo
    pick a9di923 Another meaningful message
    pick k372b37 Fix to previous typo fix

    # Rebase 12d65ea..k372b37 onto 12d65ea (4 commands)
    #
    # Commands:
    # p, pick <commit> = use commit
    # r, reword <commit> = use commit, but edit the commit message
    # e, edit <commit> = use commit, but stop for amending
    # s, squash <commit> = use commit, but meld into previous commit
    # f, fixup [-C | -c] <commit> = like "squash" but keep only the previous
    #                    commit's log message, unless -C is used, in which case
    #                    keep only this commit's message; -c is same as -C but
    #                    opens the editor**
    # x, exec <command> = run command (the rest of the line) using shell
    # b, break = stop here (continue rebase later with 'git rebase --continue')
    # d, drop <commit> = remove commit
    # l, label <label> = label current HEAD with a name
    # t, reset <label> = reset HEAD to a label
    # m, merge [-C <commit> | -c <commit>] <label> [# <oneline>]
    #         create a merge commit using the original merge commit's
    #         message (or the oneline, if no original merge commit was
    #         specified); use -c <commit> to reword the commit message
    # u, update-ref <ref> = track a placeholder for the <ref> to be updated
    #                       to this position in the new commits. The <ref> is
    #                       updated at the end of the rebase
    #
    # These lines can be re-ordered; they are executed from top to bottom.
    #
    # If you remove a line here THAT COMMIT WILL BE LOST.
    #
    # However, if you remove everything, the rebase will be aborted.
    #

Commands like pick, reword or edit are self-explanatory, but let's focus on squash and fixup. We changed order of commits and edited commands to clear history.

reordered commits

    pick    3648b69 Meaningful message
    squash  a9di923 Another meaningful message
    pick    929dbs2 Fix typo
    fixup   k372b37 Fix to previous typo fix

After saving it the window will be closed and we will be asked to edit commit message.

COMMIT_EDITMSG

# This is a combination of 2 commits.
# This is the 1st commit message:

Meaningful message

# This is the commit message #2:

# Another meaningful message

After editing it as Brand new and more meaningful message and saving it we are done. History of branch loos like this:

Info

$ git bdog master
* 132df6e (HEAD -> feature/jira1234) Fix typo
* cc0fe50 Brand new and more meaningful message

Rebase interactive in action (fixup!)

Let's say we have two commits in our branch so far.

Info

$ git bdog master
* 132df6e (HEAD -> feature/jira1234) Fix typo
* cc0fe50 Brand new and more meaningful message

So last commit is Fix typo, but we see we have a lot of typos in our code. We want to fix them but also want to achieve two contradictory things:

we want to keep (temporarily) all typo fixes in separate commits.
we want to have clean history after we are done so we will fixup all commits into one.

Let's see how we can do it and explain later.

Let's start with fixup to the specific commit.

Fixup to the specific commit

# we did some typo fixes
$ git commit -a --fixup 132df6e

We make another typo fixes and we want to fixup our last commit but we instead of checking hash of the commit we want to fixup we can use @ (is just a synonym/alias/shortcut for the special Git reference HEAD).

Fixups to the last commits

# we did another typo fixes
$ git commit -a --fixup @
# so many typos ...
$ git commit -a --fixup @

Enough typos, but our first commits needs some love too.

Fixup to the specific commit

# cc0fe50 Brand new and more meaningful message
$ git commit -a --fixup cc0fe50

This is how our git-rebase-todo history looks like now:

Info

$ git rebase -i master

pick cc0fe50 Brand new and more meaningful message
pick 132df6e Fix typo
pick 86c1657 fixup! Fix typo
pick 0a3f0a2 fixup! fixup! Fix typo
pick c15c724 fixup! Brand new and more meaningful message

We can see the naming pattern but still manual editing is needed. We are tired after fixing all those typos and we want to be done with it.

This is what we want:

Info

$ git rebase -i master

pick cc0fe50 Brand new and more meaningful message
fixup c15c724 fixup! Brand new and more meaningful message
pick 132df6e Fix typo
fixup 86c1657 fixup! Fix typo
fixup 0a3f0a2 fixup! fixup! Fix typo

Automate fixup!

We can automate this process by using git rebase -i master --autosquash. When use this command we will get the same result as above but without manual editing.

Info

$ git rebase -i master --autosquash

pick cc0fe50 Brand new and more meaningful message
fixup c15c724 fixup! Brand new and more meaningful message
pick 132df6e Fix typo
fixup 86c1657 fixup! Fix typo
fixup 0a3f0a2 fixup! fixup! Fix typo

Everything in order, everything is fixed, we are done, we can move on.

Info

$ git bdog master

pick 7a76c69 Brand new and more meaningful message
pick a4003d8 Fix typo

Real life example

example