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doc/articles/numerous_undo_possibilities_in_git/index.md
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# Numerous undo possibilities in Git
> **Article [Type](../../development/writing_documentation.html#types-of-technical-articles):** tutorial ||
> **Article [Type](../../development/writing_documentation.md#types-of-technical-articles):** tutorial ||
> **Level:** intermediary ||
> **Author:** [Crt Mori](https://gitlab.com/Letme) ||
> **Publication date:** 2017/08/04
> **Publication date:** 2017/08/17
## Introduction
In this tutorial, we will show you different ways of undoing in Git, for which
In this tutorial, we will show you different ways of undoing your work in Git, for which
we will assume you have a basic working knowledge of. Check GitLab's
[Git documentation](../../topics/git/index.md#git-documentation) for reference.
Also, we will only provide some general info of the commands, which is enough
to get you started for the easy cases/examples, but you will have to read the
command manual for anything more advanced.
to get you started for the easy cases/examples, but for anything more advanced please refer to the [Git book](https://git-scm.com/book/en/v2).
We will explain a few different techniques to undo your changes based on the stage
of the change in your current development. Also, keep in mind that [nothing in
Git is really deleted.][git-autoclean-ref]
This means that until Git automatically cleans detached commits (which cannot be
accessed by branch or tag) it will be possible to view them with `git reflog` command
and access them with direct commit-id. You can read more about [redo in below section](#redoing-the-undo).
and access them with direct commit-id. Read more about _[redoing the undo](#redoing-the-undo)_ on the section below.
This guide is organized depending on the [stage of development][git-basics]
where you want to undo your changes from and if they were shared with other developers
......@@ -78,7 +77,7 @@ proposes a solution to discard changes to certain file.
Suppose you edited a file to change the content using your favorite editor:
```
```shell
vim <file>
```
......@@ -101,19 +100,19 @@ At this point there are 3 options to undo the local changes you have:
- Discard all local changes, but save them for possible re-use [later](#quickly-save-local-changes)
```
```shell
git stash
```
- Discarding local changes (permanently) to a file
```
```shell
git checkout -- <file>
```
- Discard all local changes to all files permanently
```
```shell
git reset --hard
```
......@@ -124,7 +123,6 @@ This command resets the changes to all files, but it also saves them in case
you would like to apply them at some later time. You can read more about it in
[section below](#quickly-save-local-changes).
### Quickly save local changes
You are working on a feature when a boss drops by with an urgent task. Since your
......@@ -144,7 +142,6 @@ additional options like:
- `git stash pop`, which redoes previously stashed changes and removes them from stashed list
- `git stash apply`, which redoes previously stashed changes, but keeps them on stashed list
### Staged local changes (before you commit)
Let's say you have added some files to staging, but you want to remove them from the
......@@ -176,29 +173,28 @@ Now you have 4 options to undo your changes:
- Unstage the file to current commit (HEAD)
```
```shell
git reset HEAD <file>
```
- Unstage everything - retain changes
```
```shell
git reset
```
- Discard all local changes, but save them for [later](#quickly-save-local-changes)
```
```shell
git stash
```
- Discard everything permanently
```
```shell
git reset --hard
```
## Committed local changes
Once you commit, your changes are recorded by the version control system.
......@@ -207,7 +203,6 @@ still not public (or shared with other developers). At this point, undoing
things is a lot easier, we have quite some workaround options. Once you push
your code, you'll have less options to troubleshoot your work.
### Without modifying history
Through the development process some of the previously committed changes do not
......@@ -223,7 +218,7 @@ and `B` is the commit you want to undo. There are many different ways to identif
`B` as bad, one of them is to pass a range to `git bisect` command. The provided range includes
last known good commit (we assume `A`) and first known bad commit (where bug was detected - we will assume `E`).
```
```shell
git bisect A..E
```
......@@ -232,23 +227,23 @@ through simple bisection process. You can read more about it [in official Git To
In our example we will end up with commit `B`, that introduced bug/error. We have
4 options on how to remove it (or part of it) from our repository.
- Undo (swap additions and deletions) changes introduced by commit `B`.
- Undo (swap additions and deletions) changes introduced by commit `B`.
```
git revert commit-B-id
```
```shell
git revert commit-B-id
```
- Undo changes on a single file or directory from commit `B`, but retain them in the staged state
- Undo changes on a single file or directory from commit `B`, but retain them in the staged state
```
git checkout commit-B-id <file>
```
```shell
git checkout commit-B-id <file>
```
- Undo changes on a single file or directory from commit `B`, but retain them in the unstaged state
- Undo changes on a single file or directory from commit `B`, but retain them in the unstaged state
```
git reset commit-B-id <file>
```
```shell
git reset commit-B-id <file>
```
- There is one command we also must not forget: **creating a new branch**
from the point where changes are not applicable or where the development has hit a
......@@ -264,13 +259,12 @@ In our example we will end up with commit `B`, that introduced bug/error. We hav
![Create a new branch to avoid clashing](img/branching.png)
```
git checkout commit-B-id
git checkout -b new-path-of-feature
# Create <commit F>
git commit -a
```
```shell
git checkout commit-B-id
git checkout -b new-path-of-feature
# Create <commit F>
git commit -a
```
### With history modification
......@@ -288,34 +282,34 @@ provides interactive mode (`-i` flag) which enables you to:
Let us check few examples. Again there are commits `A-B-C-D` where you want to
delete commit `B`.
- Rebase the range from current commit D to A
- Rebase the range from current commit D to A:
```
git rebase -i A
```
```shell
git rebase -i A
```
- Command opens your favorite editor where you write `drop` in front of commit
`B`, but you leave default `pick` with all other commits. Save and exit the
editor to perform a rebase. Remember: if you want to cancel delete whole
file content before saving and exiting the editor
- Command opens your favorite editor where you write `drop` in front of commit
`B`, but you leave default `pick` with all other commits. Save and exit the
editor to perform a rebase. Remember: if you want to cancel delete whole
file content before saving and exiting the editor
In case you want to modify something introduced in commit `B`.
- Rebase the range from current commit D to A
- Rebase the range from current commit D to A:
```
git rebase -i A
```
```shell
git rebase -i A
```
- Command opens your favorite text editor where you write `edit` in front of commit
`B`, but leave default `pick` with all other commits. Save and exit the editor to
perform a rebase
- Command opens your favorite text editor where you write `edit` in front of commit
`B`, but leave default `pick` with all other commits. Save and exit the editor to
perform a rebase
- Now do your edits and commit changes
- Now do your edits and commit changes:
```
git commit -a
```
```shell
git commit -a
```
You can find some more examples in [below section where we explain how to modify
history](#how-modifying-history-is-done)
......@@ -329,7 +323,7 @@ enables you to *recall* detached local commits by referencing or applying them
via commit-id. Although, do not expect to see really old commits in reflog, because
Git regularly [cleans the commits which are *unreachable* by branches or tags][git-autoclean-ref].
To view repository history and to track older commits you can use below command
To view repository history and to track older commits you can use below command:
```shell
$ git reflog show
......@@ -352,7 +346,6 @@ in following column, number next to `HEAD` indicates how many commits ago someth
was made, after that indicator of action that was made (commit, rebase, merge, ...)
and then on end description of that action.
## Undo remote changes without changing history
This topic is roughly same as modifying committed local changes without modifying
......@@ -365,21 +358,20 @@ it also provides a clear timeline and development structure.
![Use revert to keep branch flowing](img/revert.png)
If you want to revert changes introduced in certain `commit-id` you can simply
revert that `commit-id` (swap additions and deletions) in newly created commit.
revert that `commit-id` (swap additions and deletions) in newly created commit:
You can do this with
```
```shell
git revert commit-id
```
or creating a new branch
or creating a new branch:
```
```shell
git checkout commit-id
git checkout -b new-path-of-feature
```
## Undo remote changes with modifying history
This is useful when you want to *hide* certain things - like secret keys,
......@@ -392,7 +384,6 @@ the cleanup of detached commits (happens automatically).
![Modifying history causes problems on remote branch](img/rebase_reset.png)
### Where modifying history is generally acceptable
Modified history breaks the development chain of other developers, as changed
......@@ -415,7 +406,6 @@ at merge).
>**Note:**
Never modify the commit history of `master` or shared branch
### How modifying history is done
After you know what you want to modify (how far in history or how which range of
......@@ -464,7 +454,6 @@ different outcomes locally).
git rebase -i commit-id
```
### Deleting sensitive information from commits
Git also enables you to delete sensitive information from your past commits and
......@@ -475,7 +464,7 @@ section and not as a standalone topic. To do so, you should run the
This command uses rebase to modify history and if you want to remove certain
file from history altogether use:
```
```shell
git filter-branch --tree-filter 'rm filename' HEAD
```
......@@ -486,7 +475,6 @@ An alternative is [BFG Repo-cleaner][bfg-repo-cleaner]. Keep in mind that these
tools are faster because they do not provide a same fully feature set as `git filter-branch`
does, but focus on specific usecases.
## Conclusion
There are various options of undoing your work with any version control system, but
......@@ -495,7 +483,6 @@ depending on the stage of your process. Git also enables rewriting history, but
should be avoided as it might cause problems when multiple developers are
contributing to the same codebase.
<!-- Identifiers, in alphabetical order -->
[bfg-repo-cleaner]: https://rtyley.github.io/bfg-repo-cleaner/
......@@ -508,4 +495,3 @@ contributing to the same codebase.
[gitlab-ce]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#contribution-acceptance-criteria
[gitlab-flow]: https://about.gitlab.com/2014/09/29/gitlab-flow/
[gitlab-git-tips-n-tricks]: https://about.gitlab.com/2016/12/08/git-tips-and-tricks/
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