Shallow Thoughts : tags : github

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Mon, 23 Jan 2017

Testing a GitHub Pull Request

Several times recently I've come across someone with a useful fix to a program on GitHub, for which they'd filed a GitHub pull request.

The problem is that GitHub doesn't give you any link on the pull request to let you download the code in that pull request. You can get a list of the checkins inside it, or a list of the changed files so you can view the differences graphically. But if you want the code on your own computer, so you can test it, or use your own editors and diff tools to inspect it, it's not obvious how. That this is a problem is easily seen with a web search for something like download github pull request -- there are huge numbers of people asking how, and most of the answers are vague unclear.

That's a shame, because it turns out it's easy to pull a pull request. You can fetch it directly with git into a new branch as long as you have the pull request ID. That's the ID shown on the GitHub pull request page:

[GitHub pull request screenshot]

Once you have the pull request ID, choose a new name for your branch, then fetch it:

git fetch origin pull/PULL-REQUEST_ID/head:NEW-BRANCH-NAME
git checkout NEW-BRANCH-NAME

Then you can view diffs with something like git difftool NEW-BRANCH-NAME..master

Easy! GitHub should give a hint of that on its pull request pages.

Fetching a Pull Request diff to apply it to another tree

But shortly after I learned how to apply a pull request, I had a related but different problem in another project. There was a pull request for an older repository, but the part it applied to had since been split off into a separate project. (It was an old pull request that had fallen through the cracks, and as a new developer on the project, I wanted to see if I could help test it in the new repository.)

You can't pull a pull request that's for a whole different repository. But what you can do is go to the pull request's page on GitHub. There are 3 tabs: Conversation, Commits, and Files changed. Click on Files changed to see the diffs visually.

That works if the changes are small and only affect a few files (which fortunately was the case this time). It's not so great if there are a lot of changes or a lot of files affected. I couldn't find any "Raw" or "download" button that would give me a diff I could actually apply. You can select all and then paste the diffs into a local file, but you have to do that separately for each file affected. It might be, if you have a lot of files, that the best solution is to check out the original repo, apply the pull request, generate a diff locally with git diff, then apply that diff to the new repo. Rather circuitous. But with any luck that situation won't arise very often.

Update: thanks very much to Houz for the solution! (In the comments, below.) Just append .diff or .patch to the pull request URL, e.g. https://github.com/OWNER/REPO/pull/REQUEST-ID.diff which you can view in a browser or fetch with wget or curl.

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[ 14:34 Jan 23, 2017    More programming | permalink to this entry | comments ]

Tue, 05 Apr 2016

Modifying a git repo so you can pull without a password

There's been a discussion in the GIMP community about setting up git repos to host contributed assets like scripts, plug-ins and brushes, to replace the long-stagnant GIMP Plug-in Repository. One of the suggestions involves having lots of tiny git repos rather than one that holds all the assets.

That got me to thinking about one annoyance I always have when setting up a new git repository on github: the repository is initially configured with an ssh URL, so I can push to it; but that means I can't pull from the repo without typing my ssh password (more accurately, the password to my ssh key).

Fortunately, there's a way to fix that: a git configuration can have one url for pulling source, and a different pushurl for pushing changes.

These are defined in the file .git/config inside each repository. So edit that file and take a look at the [remote "origin"] section.

For instance, in the GIMP source repositories, hosted on git.gnome.org, instead of the default of url = ssh://git.gnome.org/git/gimp I can set

pushurl = ssh://git.gnome.org/git/gimp
url = git://git.gnome.org/gimp
(disclaimer: I'm not sure this is still correct; my gnome git access stopped working -- I think it was during the Heartbleed security fire drill, or one of those -- and never got fixed.)

For GitHub the syntax is a little different. When I initially set up a repository, the url comes out something like url = git@github.com:username/reponame.git (sometimes the git@ part isn't included), and the password-free pull URL is something you can get from github's website. So you'll end up with something like this:

pushurl = git@github.com:username/reponame.git
url = https://github.com/username/reponame.git

Automating it

That's helpful, and I've made that change on all of my repos. But I just forked another repo on github, and as I went to edit .git/config I remembered what a pain this had been to do en masse on all my repos; and how it would be a much bigger pain to do it on a gazillion tiny GIMP asset repos if they end up going with that model and I ever want to help with the development. It's just the thing that should be scriptable.

However, the rules for what constitutes a valid git passwordless pull URL, and what constitutes a valid ssh writable URL, seem to encompass a lot of territory. So the quickie Python script I whipped up to modify .git/config doesn't claim to handle everything; it only handles the URLs I've encountered personally on Gnome and GitHub. Still, that should be useful if I ever have to add multiple repos at once. The script: repo-pullpush (yes, I know it's a terrible name) on GitHub.

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[ 12:28 Apr 05, 2016    More programming | permalink to this entry | comments ]

Thu, 19 Mar 2015

Hints on migrating Google Code to GitHub

Google Code is shutting down. They've sent out notices to all project owners suggesting they migrate projects to other hosting services.

I moved all my personal projects to GitHub years ago, back when Google Code still didn't support git. But I'm co-owner on another project that was still hosted there, and I volunteered to migrate it. I remembered that being very easy back when I moved my personal projects: GitHub had a one-click option to import from Google Code. I assumed (I'm sure you know what that stands for) that it would be just as easy now.

Nope. Turns out GitHub no longer has any way to import from Google Code: it tells you it can't find a repository there when you give it the address to Google's SVN repository.

Google's announcement said they were providing an exporter to GitHub. So I tried that next. I had the new repository ready on GitHub -- under the owner's account, not mine -- and I expected Google's exporter to ask me for the repository.

Not so. As soon as I gave it my OAuth credentials, it immediately created a new repository on GitHub under my name, using the name we had used on Google Code (not the right name, since Google Code project names have to be globally unique while GitHub projects don't).

So I had to wait for the export to finish; then, on GitHub, I went to our real repository, and did an import there from the new repository Google had created under my name. I have no idea how long that took: GitHub's importer said it would email me when the import was finished, but it didn't, so I waited several hours and decided it was probably finished. Then I deleted the intermediate repository.

That worked fine, despite being a bit circuitous, and we're up and running on GitHub now.

If you want to move your Google Code repository to GitHub without the intermediate step of making a temporary repository, or if you don't want to give Google OAuth access to your GitHub account, here are some instructions (which I haven't tested) on how to do the import via a local copy of the repo on your own machine, rather than going directly from Google to GitHub: krishnanand's steps for migrating Google code to GitHub

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[ 13:11 Mar 19, 2015    More programming | permalink to this entry | comments ]