Exercise - Reverting
Git allows changes made in an earlier commit to be undone by a new commit.
Info
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git revert <commit>creates a new commit, which undoes the changes of an earlier commit. -
With a merge commit you must also specify to which merge parent the determination of the changes should refer:
git revert -m 1 <merge-commit> -
With commits further back, conflicts can occur (because affected files were further edited in later commits). These must then be resolved like merge conflicts.
Example setup
In the example repository, a file was renamed, the corresponding commit is tagged with umbenennung.
In addition, a feature branch was integrated via merge. The merge commit is tagged with feature-merge.
Both changes are to be undone.
Step 0 - START
$ cd repo
Step 1 - Undo a single commit.
Start in directory git-uebungen/aufgaben/<unknown>.
In the history, the file README.md was renamed to liesmich. Undo this change. Tip: The commit is tagged as umbenennung.
Step 2 - Undo merge commit.
Start in directory git-uebungen/aufgaben/<unknown>.
In the history, a feature branch was integrated via merge.file . Undo this change. Tip: The merge commit is tagged as feature-merge. Tip: The success can be recognized by the disappearance of the file from-feature.
Step 3 - Feature branch broken!?
Start in directory git-uebungen/aufgaben/<unknown>.
A revert is often used to temporarily roll back a feature, e.g. due to a production problem. Later you want to correct the feature branch and then integrate it again. This is not so easy.
In the example, the feature branch has undergone further development. Try to merge it again. Examine the error message and the commit graph. Tip: The failed merge can be aborted with git merge --abort.
Step 4 - Undo merge revert again.
Start in directory git-uebungen/aufgaben/<unknown>.
The trick is to revert the revert commit itself, then those changes are back on which the further development of the feature is based.
Tip: The commit is tagged as feature-merge.
repo $ cd ..