You are happily working on something, and find the changes in these files are in good order. You do not want to see them when you run git diff, because you plan to work on other files and changes with these files are distracting.

Somebody asks you to pull, and the changes sound worthy of merging.

However, you already dirtied the index (i.e. your index does not match the HEAD commit). But you know the pull you are going to make does not affect frotz.c or filfre.c, so you revert the index changes for these two files. Your changes in working tree remain there.

Then you can pull and merge, leaving frotz.c and filfre.c changes still in the working tree.

This is most often done when you remembered what you just committed is incomplete, or you misspelled your commit message, or both. Leaves working tree as it was before "reset".

Make corrections to working tree files.

"reset" copies the old head to .git/ORIG_HEAD; redo the commit by starting with its log message. If you do not need to edit the message further, you can give -C option instead.

You have made some commits, but realize they were premature to be in the master branch. You want to continue polishing them in a topic branch, so create topic/wip branch off of the current HEAD.

Rewind the master branch to get rid of those three commits.

Switch to topic/wip branch and keep working.

The last three commits (HEAD, HEAD^, and HEAD~2) were bad and you do not want to ever see them again. Do not do this if you have already given these commits to somebody else. (See the "RECOVERING FROM UPSTREAM REBASE" section in git-rebase[1] for the implications of doing so.)

Try to update from the upstream resulted in a lot of conflicts; you were not ready to spend a lot of time merging right now, so you decide to do that later.

"pull" has not made merge commit, so git reset --hard which is a synonym for git reset --hard HEAD clears the mess from the index file and the working tree.

Merge a topic branch into the current branch, which resulted in a fast-forward.

But you decided that the topic branch is not ready for public consumption yet. "pull" or "merge" always leaves the original tip of the current branch in ORIG_HEAD, so resetting hard to it brings your index file and the working tree back to that state, and resets the tip of the branch to that commit.

Even if you may have local modifications in your working tree, you can safely say git pull when you know that the change in the other branch does not overlap with them.

After inspecting the result of the merge, you may find that the change in the other branch is unsatisfactory. Running git reset --hard ORIG_HEAD will let you go back to where you were, but it will discard your local changes, which you do not want. git reset --merge keeps your local changes.

This commit will get blown away so a throw-away log message is OK.

This removes the WIP commit from the commit history, and sets your working tree to the state just before you made that snapshot.

At this point the index file still has all the WIP changes you committed as snapshot WIP. This updates the index to show your WIP files as uncommitted.

This removes the file from the index while keeping it in the working directory.

This commits all other changes in the index.

Adds the file to the index again.

This commits your first edits in branch1.

In the ideal world, you could have realized that the earlier commit did not belong to the new topic when you created and switched to branch2 (i.e. git switch -c branch2 start), but nobody is perfect.

But you can use reset --keep to remove the unwanted commit after you switched to branch2.

First, reset the history back one commit so that we remove the original commit, but leave the working tree with all the changes. The -N ensures that any new files added with HEAD are still marked so that git add -p will find them.

Next, we interactively select diff hunks to add using the git add -p facility. This will ask you about each diff hunk in sequence and you can use simple commands such as "yes, include this", "No don’t include this" or even the very powerful "edit" facility.

Once satisfied with the hunks you want to include, you should verify what has been prepared for the first commit by using git diff --cached. This shows all the changes that have been moved into the index and are about to be committed.

Next, commit the changes stored in the index. The -c option specifies to pre-populate the commit message from the original message that you started with in the first commit. This is helpful to avoid retyping it. The HEAD@{1} is a special notation for the commit that HEAD used to be at prior to the original reset commit (1 change ago). See git-reflog[1] for more details. You may also use any other valid commit reference.

You can repeat steps 2-4 multiple times to break the original code into any number of commits.

Now you’ve split out many of the changes into their own commits, and might no longer use the patch mode of git add, in order to select all remaining uncommitted changes.

Once again, check to verify that you’ve included what you want to. You may also wish to verify that git diff doesn’t show any remaining changes to be committed later.

And finally create the final commit.