Git Patching Questions

[cbkazl]

Hello,
I'm fairly new to git so I have a few questions regarding patches.

I have been experimenting with the crawl code by adding in a new species, and after a bit of trial and error, committed some additions and made a patch out of them. However, I found a few whitespace errors my code and while they were simple to fix, I am having trouble applying these fixes to my patch.

The best I can do is commit the fixes and make a new patch out of them, which gives me two patches, one with the changes, and one with the fix to the changes. How do I just 'update' my first patch to have the fixes?


Another question: How would I go about 'uncommitting' my changes to the code? I would like to test if applying the patch to a fresh install would work. I could clone the crawl code again, but is there a better way?

[MDvedh]

You should use

  Code:

 $ git commit amend

it will merge new changes with your last commit.

[CommanderC]

You should learn how to use branches. They will solve all your problems.

Branches are like different versions or variants of a project, but only one of them can be active at the same time (e.g. the current files in your hd belong to that branch). Each time you commit some changes to a project, they are actually applied only to the current branch.

To see the list of local branches, and which one is the current one:

  Code:

$ git branch

To create a new branch:

  Code:

$ git branch branch-name

To switch to another branch:

  Code:

$ git checkout branch-name

Thanks to branches you won't need to 'uncommit' anything, and creating patches will be easier. Make sure you never commit changes to the master branch. That one is linked to a remote repository. Commit them to a new branch, and then:

  Code:

$ git format-patch master

[cbkazl]

Thanks for the tips. It looks like that will solve all my problems.

[galehar]

To update your latest commit, add the new changes (git add foo.cc), then amend the commit (git commit --amend).
To merge the last 2 commits together, use interactive rebase: git rebase -i HEAD~2. Then, change the second commit to squash or fixup.

[Marbit]

I'm also learning how to use git.
If I understood correctly what happens in a branch stays in a branch.
Still I'm having touble with that, am I doing something wrong?

  Code:

echo "Example crawl code" > crawl_file
git add crawl_file
git branch new_branch
git checkout new_branch
echo "New code line" >> crawl_file
git checkout master

#Here I'm in the master.
#Why do I see changes made in new_branch?
cat crawl_file
>Example crawl code
>New code line

Edit: added line "git add crawl_file"

[Cedor]

You must commit your changes before changing branch.

Once the commit is done, it becomes part of the branch. And all non commited changes are transfered to the new branch when you switch via checkout.

[Marbit]

As a follow up I commited a change... but then when trying to switch to the master branch it seems I didn't.

  Code:

echo "Example crawl code" > crawl_file
git add crawl_file
git branch new_branch
git checkout new_branch
echo "New code line" >> crawl_file
#Let's commit the changes
git commit -m "hopefully changes won't be in master branch"
git checkout master

>error: Your local changes to the following files would be overwritten by checkout:
>crawl-ref/source/crawl_file
>Please, commit your changes or stash them before you can switch branch
>Aborting

#WTF! I thought that I had already commited my changes!

[Cedor]

My bad.

You must add the files you made changes on and then commit it. I'm a user of the short instruction (git commit -a) but manualy specifing wich files you want to add to your commit is safer.

[CKyle]

As a follow up I commited a change... but then when trying to switch to the master branch it seems I didn't.

If you're still in new_branch right now, run

  Code:

git diff

You should see the addition of "New code line" in the diff output. What happened is that when you ran "git add crawl_file", you told it to commit the version of the file present at the time you ran that command. You then committed that version in the "new_branch" branch.

However, your addition of "New code line" was never added or committed. Checking out master would restore a version of your local directory that does not include crawl_file at all, much less "New code line". You'll have to run

  Code:

git add crawl_file

again and then

  Code:

git commit

for that new line to be saved.

Generally, you only want to run "git add [filename]" when the file is exactly how you want it to be committed. If you run it multiple times on the same file before committing, it will commit the last version of the file you give it.