How to undo the last git commit?

There are situations where you just committed a change in git and just after that realized you made a mistake in the last commit. If you haven’t pushed that code then the last local changes can be undone with the following command.

git reset --soft HEAD~1

What this does is that it uncommits the last change and puts that back in a staged state. That means if you run the git status command then you will see those changes in your working directory. Now you can make further changes to that revision and then commit again.

Creating Git branch in detached HEAD State

Recently, I came across a situation where I checked out a git branch and it showed me this message:

You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by performing another checkout.

I guess this happened because the branch that I was checking out was rebased. Otherwise, it usually happens when you checkout a commit with its hash. But in my case, I was checking out a branch. Anyway, this is a special state called “detached HEAD”. While you can commit changes in this state, those commits don’t belong to any branch and will become inaccessible as soon as you check out another branch. But what if you do want to keep those commits?

The answer, unsurprisingly, is to use the “checkout” command again and you can use the same branch again:

git checkout <branch> #now you're in detached head state
# do some work and stage it
git add --all
git commit -m "add some work while in detached head state"
git branch <branch>
git checkout <branch>

Pretty easy, right?

Codenvy and BitBucket Integration

OK, this post is a quick one. Let’s go.

In your Codenvy workspace goto Profile > Preferences > SSH > VCS and generate key and give it a name bitbucket.org. This will generate key for you. Copy this key by viewing it which we will use later on BitBucket.

Now go to BitBucket, select your repository, and then goto repository settings. Under Access Keys menu click Add Key button. Give a label as bitbucket.org and paste the key copied in previous step here and save.

Now on Codenvy project goto Git menu and add remote. You need to give SSH url to your BitBucket repo here. Add it and you can now pull the repo from BitBucket. Awesome!

Deploy your first ASP.Net MVC App to AppHarbor

If you’ve been developing ASP.Net MVC apps lately you might be thinking some online or cloud based app hosting platform available as PaaS for Microsoft technologies specially for hosting ASP.Net MVC apps just like OpenShift, Heroku and other platforms are available for technologies like Ruby, Python, PHP, Node.js and even supporting CMS like WordPress. The good news for ASP.Net developers is that there is a PaaS platform available which you might already know. The platform is AppHarbor. AppHarbor runs over Amazon AWS and has some nice features that I won’t go into the details of. If you are interested in knowing how AppHarbor works you can see their page here.

Regardless of AppHarbor provides a decent service, new developers might still face some difficulty in deploying their applications to AppHarbor. Specially, if you are developing apps based on new Visual Studio 2015 templates like MVC. Their are different ways to deploy but I would follow below approach which in my opinion is good and provide auto deployment or in other words Continuous Integration (CI).

What you need?

We will be using following tools and accounts.

  • Visual Studio 2015 (any edition, I used Professional version)
  • ASP.Net MVC app created from VS2015 MVC template
  • GitHub repo for the app/project
  • Local git repo for app with remote repo set as your GitHub app repo
  • AppHarbor app

What’s not covered?

Our focus today is deployment of our ASP.Net MVC app to AppHarbor. Therefore, we won’t be going into the details of how application is created or its architecture, what’s new in Visual Studio 2015, what is MVC, what is Git and GitHub, and how to connect your GitHub repo to AppHarbor etc. We will assume that you already have all the pre-requisites and we will just focus what problems can we come across during deployment and how to fix them.

Deployment Steps

  1. Initialize a Git repo and connect it with your GitHub repo.
  2. Create AppHarbor app from your GitHub repo. Whenever we commit/push our changes to our GitHub repo AppHarbor will automatically fetches the latest push and build it. Upon successful build it will deploy the app on its server otherwise it will keep last successful build. This makes things very easy.
  3. Create an ASP.Net MVC application using Visual Studio 2015 MVC template.
  4. Add the packages folder to .gitignore
  5. Enable NuGet Package Restore. In VS2015 click Tools>Options and then select NuGet Package Manager and make sure both checkboxes are checked in this section.
  6. In VS2015 right click on project and click properties, then goto Build Events tab. In the Post-build event command line text area paste the following command.
    1. if not exist “$(WebProjectOutputDir)\bin\Roslyn” md “$(WebProjectOutputDir)\bin\Roslyn”
      start /MIN xcopy /s /y /R “$(OutDir)roslyn\*.*” “$(WebProjectOutputDir)\bin\Roslyn”
  7. Now commit and push your changes to GitHub.
  8. That’s it! AppHarbor will automatically fetch the latest version changes and build it and you can check your AppHarbor application on its URL.

What’s Next?

There are few things that you need to take care of specially related to security. This MVC app uses SQL Server Compact which isn’t a good option for production level apps. Secondly, your connection string or password to database must not be committed to public GitHub repo.

This post will just give you smooth start without any difficulties which I faced among other people that you can see in the resources section below.

If you think this was helpful or if I have missed anything please do let me know in the comments below.

Happy coding!

Resources

  1. https://blog.appharbor.com/2012/02/06/use-nuget-package-restore-to-avoid-pushing-packages-to-appharbor
  2. https://support.appharbor.com/discussions/problems/79727-error-msb3202-when-building
  3. https://support.appharbor.com/discussions/problems/78633-cant-build-aspnet-mvc-project-generated-from-vstudio-2015-enterprise#comment_37577678

git – the simple guide

create a new repository

create a new directory, open it and perform a
git init
to create a new git repository.

checkout a repository

create a working copy of a local repository by running the command
git clone /path/to/repository
when using a remote server, your command will be
git clone [email protected]:/path/to/repository

workflow

your local repository consists of three “trees” maintained by git. the first one is your Working Directory which holds the actual files. the second one is the Index which acts as a staging area and finally theHEAD which points to the last commit you’ve made.

add & commit

You can propose changes (add it to the Index) using
git add <filename>
git add *
This is the first step in the basic git workflow. To actually commit these changes use
git commit -m "Commit message"
Now the file is committed to the HEAD, but not in your remote repository yet.

pushing changes

Your changes are now in the HEAD of your local working copy. To send those changes to your remote repository, execute
git push origin master
Change master to whatever branch you want to push your changes to.

If you have not cloned an existing repository and want to connect your repository to a remote server, you need to add it with
git remote add origin <server>
Now you are able to push your changes to the selected remote server

branching

Branches are used to develop features isolated from each other. Themaster branch is the “default” branch when you create a repository. Use other branches for development and merge them back to the master branch upon completion.

create a new branch named “feature_x” and switch to it using
git checkout -b feature_x
switch back to master
git checkout master
and delete the branch again
git branch -d feature_x
a branch is not available to others unless you push the branch to your remote repository
git push origin <branch>

update & merge

to update your local repository to the newest commit, execute
git pull
in your working directory to fetch and merge remote changes.
to merge another branch into your active branch (e.g. master), use
git merge <branch>
in both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in conflicts. You are responsible to merge those conflicts manually by editing the files shown by git. After changing, you need to mark them as merged with
git add <filename>
before merging changes, you can also preview them by using
git diff <source_branch> <target_branch>

tagging

it’s recommended to create tags for software releases. this is a known concept, which also exists in SVN. You can create a new tag named 1.0.0by executing
git tag 1.0.0 1b2e1d63ff
the 1b2e1d63ff stands for the first 10 characters of the commit id you want to reference with your tag. You can get the commit id by looking at the…

log

in its simplest form, you can study repository history using.. git log
You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author:
git log --author=bob
To see a very compressed log where each commit is one line:
git log --pretty=oneline
Or mabe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches:
git log --graph --oneline --decorate --all
See only which files have changed:
git log --name-status
These are just a few of the possible parameters you can use. For more, see git log --help

replace local changes

In case you did something wrong (which for sure never happens 😉 you can replace local changes using the command
git checkout -- <filename>
this replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, as well as new files, will be kept.

If you instead want to drop all your local changes and commits, fetch the latest history from the server and point your local master branch at it like this
git fetch origin
git reset --hard origin/master

useful hints

built-in git GUI
gitk
use colorful git output
git config color.ui true
show log on just one line per commit
git config format.pretty oneline
use interactive adding
git add -i