05 Version Control.md

Version Control

1. Git Remotes *
2. Branching
3. GitFlow

1 Git Remotes

git clone https://github.coventry.ac.uk/304CEM-1718SEPJAN/currency.git

$ git config user.name "John Doe"
$ git config user.email johndoe@example.com
$ git config core.editor 'nano'
$ git config credential.helper cache
$ git config credential.helper 'cache --timeout=3600'
$ git config --list
  credential.helper=cache --timeout=3600
  core.editor=nano
  user.name=John Doe
  user.email=johndoe@example.com

1.1 Commits

$ git log
commit 51f469eb41eb486c4316a97e7badc0ec9af36cb5
Author: Mark Tyers <aa7401@coventry.ac.uk>
Date:   Mon Jun 12 10:24:18 2017 +0100

    renamed files

commit d3ef104463d3bb33b8b8862fe986e8b93038ade3
Author: Mark Tyers <aa7401@coventry.ac.uk>
Date:   Mon Jun 12 07:45:22 2017 +0100

    added start of gitflow

You navigate using space for the next page, w for the previous page and q to quit.

1.2 Remotes

$ git remote show
  origin
$ git remote get-url origin
  https://github.coventry.ac.uk/304CEM-1718SEPJAN/TEACHING-MATERIALS.git

2 Branching

List branches.

$ git branch
  * master

Display the branch structure in the log output:

git log --graph --abbrev-commit --decorate
  * commit 37cedee
  | Author: Mark Tyers <marktyers@gmail.com>
  | Date:   Sat May 27 10:45:54 2017 +0100
  |
  |     chapter 1 structure done
  |
  *   commit e90e847
  |\  Merge: 7b4e193 5a2aaad
  | | Author: Mark Tyers <marktyers@gmail.com>
  | | Date:   Sat May 27 08:38:00 2017 +0100
  | |
  | |     added more samples
  | |
  | * commit fa37b77
  | | Author: Mark Tyers <marktyers@gmail.com>
  | | Date:   Mon May 15 13:35:34 2017 +0100
  | |
  | |     completed first example
  | |
  * | commit 7b4e193
  |/  Author: Mark Tyers <marktyers@gmail.com>
  |   Date:   Sat May 27 08:35:07 2017 +0100
  |
  |       minor changes
  |
  * commit 40f08a9
  | Author: Mark Tyers <marktyers@gmail.com>
  | Date:   Sun May 14 15:50:00 2017 +0100
  |
  |     added content to chapter 1
  |

$ git log --graph --abbrev-commit --decorate --pretty=oneline
  * 480d68b chapter 2 structure complete
  * 37cedee chapter 1 structure done
  *   e90e847 added more samples
  |\
  | * 5a2aaad week 2 structure
  | * 085df46 finished chapter 1
  | * fa37b77 completed first example
  * | 7b4e193 minor changes
  |/
  * 40f08a9 added content to chapter 1

$ git log --all --decorate --oneline --graph
  * 37cedee chapter 1 structure done
  *   e90e847 added more samples
  |\
  | * 5a2aaad week 2 structure
  | * 085df46 finished chapter 1
  | * fa37b77 completed first example
  * | 7b4e193 minor changes
  |/
  * 40f08a9 added content to chapter 1

Remote Tracking Branches

If you check out a local branch Git automaticall creates a tracking branch which is a local branch that has a direct relationship with a remote branch. This is why Git knows which branch to use when you run git pull. These branches are read-only and act as bookmarks to where your remote branches were last time you connected to them.

$ git branch --all
  * master
    remotes/origin/HEAD -> origin/master
    remotes/origin/master

You can get a list of the commits on the remote branch git log origin/master

TODO

3 Git Flow

GitFlow is a Git branching model developed by Vincent Driessen and is especially useful if you are collaborating with others and/or indending to implement either continuous integration or continuous deployment. It is assumed that you are comfortable

The GitFlow branching model makes use of Git branches to provide a robust way to develop and deploy stable code by imposing a rigid approach in the use of branches. To support this, there is a git plugin which should be installed.

sudo apt-get install git-flow

Once the plugin is installed it provides a number of custom commands.

               A                             H    K           N
MASTER      ───⬤────────────────────────────⬤───⬤──────────⬤────
                │                            │    │  L    M   │
HOTFIX a        │                            │    ╰──⬤───⬤──┤
                │                         G  │                │
RELEASE 1.1     │                     ╭──⬤──┤                │
                │  B           E      │      │                │
DEVELOP         └──⬤──────────⬤─────⬤─────⬤───────────────⬤────
                    │  C    D   │     F      J                P
FEATURE A           ╰──⬤───⬤──╯ 

The diagram above shows a typical set of branches used in GitFlow. The first thing you will notice is that there are two historical branches (ones that always exist). By default these are called master and develop. All the development takes place in the development branch with the master branch reserved for production-level code ready for release. When you initialise GitFlow on your project it will add this develop branch (A).

Since development happens in the develop branch, all feature branches originate from here (B) and once a feature is complete and fully tested it is merged back to the develop branch (E).

The process of releasing code is carried out by creating a release branch (F) and all final tests and bugfixes are carried out here (G). Once the team is happy that there are no more bugs and the code is ready for deployment, this branch is merged into both the master branch (H) but also back into the develop branch (J) so that any changes are available to the developers.

If any bugs are found in the master branch, a hotfix branch is created off the master branch (K), the bugs are fixed (L) (M) then the changes are merged back in to the master branch (N) and the develop branch (P).

6.1 Test Your Knowledge

git clone https://github.coventry.ac.uk/304CEM-1718SEPJAN/currency.git gitflow

1. Performing Git setup (name, email, editor, cache)
2. Install GitFlow sudo apt-get install git-flow
3. Initialise GitFlow git flow init, accepting the defaults for all the options.

$ git flow init
  Which branch should be used for bringing forth production releases?
     - master
  Branch name for production releases: [master] 
  Branch name for "next release" development: [develop] 

  How to name your supporting branch prefixes?
  Feature branches? [feature/] 
  Bugfix branches? [bugfix/] 
  Release branches? [release/] 
  Hotfix branches? [hotfix/] 
  Support branches? [support/] 
  Version tag prefix? [] 
  Hooks and filters directory? [/home/marktyers/Documents/currency/.git/hooks] 

If we list all the branches we will see that we still have the master branch and its matching remote but we now have a new local branch called develop and that this is the branch that is currently checked out:

$ git branch -a
  * develop
    master
    remotes/origin/master

The next step is to implement the three features, each will be in its own feature branch, the suggested branch names are shown:

1. modify the script to ask for the currency to convert to and display only the one conversion rate (display-single-currency).
2. instead of printing the exchange rate, ask for the amount to be converted and them return the equivalent in the chosen currency (ask-for-amount)
3. use the OpenExchangeRates API to display the full name of the chosen currency (show-full-currency-name).

$ git flow feature start display-single-currency
  Switched to a new branch 'feature/display-single-currency'

  Summary of actions:
  - A new branch 'feature/display-single-currency' was created, based on 'develop'
  - You are now on branch 'feature/display-single-currency'

If we list our local branches you will see that there is a new branch and that it has been checked out.

$ git branch
    develop
  * feature/display-single-currency
    master

Your next step is to implement the feature. Remember to commit your code on a regular basis, you should aim to do at least 2 commits.

If you plan on collaborating with other developers on this feature you will need to publish it. This will push the branch to your GitHub remote which means it will be available for the other developers to use. If you don't publish it it won't be visible on your GitHub remote.

git flow feature publish display-single-currency

Once the feature is completed you can finish the feature. This will open our default code editor (we specified the nano editor), accept the default commit message then save and quit the editor using ctrl+o and ctrl+x.

$ git flow feature finish display-single-currency
  Switched to branch 'develop'
  Merge made by the 'recursive' strategy.
   index.js   | 27 ++++++++++++++++++++-------
   3 files changed, 72 insertions(+), 7 deletions(-)
   create mode 100644 .eslintrc
   create mode 100644 .gitignore
  Deleted branch feature/display-single-currency (was cd5b304).

  Summary of actions:
  - The feature branch 'feature/display-single-currency' was merged into 'develop'
  - Feature branch 'feature/display-single-currency' has been locally deleted
  - You are now on branch 'develop'

Viewing the commit log you will see something like the following:

$ git log --all --decorate --oneline --graph
*   5928d5e (HEAD -> develop) Merge branch 'feature/display-single-currency' into develop
|\
| * cd5b304 prints single conversion rate
| * 4b6d5f0 isolates single currency
|/
* a443a19 (origin/master, master) Added main script file

As you can see, the new branch comes off the develop branch and then merged back into develop and the feature branch deleted.

Repeat this for the other two features ensuring you create a new branch for each of them.

Release

Once the features are implemented and tested it is time to create a release 1.0.0 using the features of GitFlow.

$ git flow release start 1.0.0
  Switched to a new branch 'release/1.0.0'

  Summary of actions:
  - A new branch 'release/1.0.0' was created, based on 'develop'
  - You are now on branch 'release/1.0.0'

  Follow-up actions:
  - Bump the version number now!
  - Start committing last-minute fixes in preparing your release
  - When done, run:

       git flow release finish '1.0.0'

If we list the local branches we will see that the feature branch is no longer available and that there is a new branch we will be using to finalise the release.

$ git branch
  develop
  master
* release/1.0.0

If you want other developers to work on the release you will need to publish it. This will push the branch to your GitHub remote which means it will be available for the other developers to use. If you don't publish it it won't be visible on your GitHub remote.

git flow release publish '1.0.0'

When we carry out the final tests on our code we notice that it fails to exit cleanly when the script finishes. This is an issue that needs to be fixed before we can release the product to our end users! The solution is to include the following command immediately after the script displays the results to the user.

process.exit()

Add this line, test and then make a commit.

Now we can finish the release.

You will be prompted for the commit message (use the default) and will also be asked to provide a tag name, use v1.0.0.

$ git flow release finish '1.0.0'
  Switched to branch 'master'
  Your branch is up-to-date with 'origin/master'.
  Merge made by the 'recursive' strategy.
   index.js   | 28 +++++++++++++++++++++-------
   1 file changed, 28 insertions(+), 7 deletions(-)
   create mode 100644 .eslintrc
   create mode 100644 .gitignore
  Already on 'master'
  Your branch is ahead of 'origin/master' by 7 commits.
    (use "git push" to publish your local commits)
  Switched to branch 'develop'
  Merge made by the 'recursive' strategy.
   index.js | 1 +
   1 file changed, 1 insertion(+)
  Deleted branch release/1.0.0 (was 1677906).

  Summary of actions:
  - Release branch 'release/1.0.0' has been merged into 'master'
  - The release was tagged '1.0.0'
  - Release tag '1.0.0' has been back-merged into 'develop'
  - Release branch 'release/1.0.0' has been locally deleted
  - You are now on branch 'develop'

If we look at the commit graph we will see the entire commit history (yours will be longer than this:

$ git log --all --decorate --oneline --graph
  *   df496c8 (develop) Merge tag '1.0.0' into develop
  |\
  | *   12fe99c (HEAD -> master, tag: 1.0.0) Merge branch 'release/1.0.0'
  | |\
  | | * 1677906 fixed issue of script not exiting cleanly
  | |/
  |/|
  * |   5928d5e Merge branch 'feature/display-single-currency' into develop
  |\ \
  | |/
  |/|
  | * cd5b304 prints single conversion rate
  | * 4b6d5f0 isolates single currency
  |/
  * a443a19 (origin/master) Added main script file

And if we checkout the master branch we will see that it contains our working code including the release code.

Hotfixes

Try running the script and input an invalid code, what happens. The chances are that the error message is printed but then the script continues to execute! This is a serious but in our release code and we will need to implement a hotfix.

$ git flow hotfix start '1.0.1'
  Switched to a new branch 'hotfix/1.0.1'

  Summary of actions:
  - A new branch 'hotfix/1.0.1' was created, based on 'master'
  - You are now on branch 'hotfix/1.0.1'

  Follow-up actions:
  - Start committing your hot fixes
  - Bump the version number now!
  - When done, run:

       git flow hotfix finish '1.0.1'

Now you need to fix the issue by adding the line process.exit() to each error handling block. Once you have finished, you need to commit the changes and then finish the hotfix. Use the tag v1.0.1.

$ git flow hotfix finish '1.0.1'
  Branches 'master' and 'origin/master' have diverged.
  And local branch 'master' is ahead of 'origin/master'.
  Switched to branch 'master'
  Your branch is ahead of 'origin/master' by 7 commits.
    (use "git push" to publish your local commits)
  Merge made by the 'recursive' strategy.
   index.js    | 57 +++++++++++++++++++++++++++++++--------------------------
   1 file changed, 7 insertions(+), 7 deletions(-)
   create mode 100644 solution.js
  Switched to branch 'develop'
  Merge made by the 'recursive' strategy.
   index.js    | 57 +++++++++++++++++++++++++++++++--------------------------
   1 file changed, 7 insertions(+), 7 deletions(-)
   create mode 100644 solution.js
  Deleted branch hotfix/v1.0.1 (was 725b3ca).

  Summary of actions:
  - Hotfix branch 'hotfix/v1.0.1' has been merged into 'master'
  - The hotfix was tagged 'v1.0.1'
  - Hotfix tag 'v1.0.1' has been back-merged into 'develop'
  - Hotfix branch 'hotfix/v1.0.1' has been locally deleted
  - You are now on branch 'develop'

If you switch between the develop and master branches you will see that your hotfix has been applied to both.

Pushing the Tags

By default, all the tags are local only and don't get pushed to your GitHub remote. Lets start by listing the local tags.

$ git tag
  1.0.0
  1.0.1

And to see the tags on the remote (this returns nothing).

$ it ls-remote --tags origin

To push our tags to the remote.

$ git push origin --tags

$ git ls-remote --tags origin
  dd94793b69a8307157baf82011edfb2607b9b17a        refs/tags/1.0.0
  12fe99ca9326b10b54f1a06ccda7724694791e9d        refs/tags/1.0.0^{}
  0f3fbe765b99cab3039d35d8bdfdd912d5e5a9fa        refs/tags/v1.0.1
  53babbaeeb07a49def0e77405576a6a316750a8e        refs/tags/v1.0.1^{}

If you are using GitHub, these tags can be accessed under the releases tab where the tagged code can be downloaded.