<p>Suppose your git history looks like this:</p>

<p>1
2
3
4
5</p>

<p>1–5 are separate revisions. You need to remove 3 while still keeping 1, 2, 4 and 5. How can this be done?</p>

<p>Is there an efficient method when there are hundreds of revisions after the one to be deleted?</p>

To combine revision 3 and 4 into a single revision, you can use git rebase. If you want to remove the changes in revision 3, you need to use the edit command in the interactive rebase mode. If you want to combine the changes into a single revision, use squash.
I have successfully used this squash technique, but have never needed to remove a revision before. The git-rebase documentation under "Splitting commits" should hopefully give you enough of an idea to figure it out. (Or someone else might know).
From the
git documentation
:
Start it with the oldest commit you want to retain as-is:
```
git rebase -i <after-this-commit>
```
An editor will be fired up with all the commits in your current branch (ignoring merge commits), which come after the given commit. You can reorder the commits in this list to your heart's content, and you can remove them. The list looks more or less like this:
```
pick deadbee The oneline of this commit
pick fa1afe1 The oneline of the next commit
...
```
The oneline descriptions are purely for your pleasure; git-rebase will not look at them but at the commit names ("deadbee" and "fa1afe1" in this example), so do not delete or edit the names.
By replacing the command "pick" with the command "edit", you can tell git-rebase to stop after applying that commit, so that you can edit the files and/or the commit message, amend the commit, and continue rebasing.
If you want to fold two or more commits into one, replace the command "pick" with "squash" for the second and subsequent commit. If the commits had different authors, it will attribute the squashed commit to the author of the first commit.