Get started with fledge

library(fledge)

The goal of {fledge} is to streamline the process of versioning R packages and updating the NEWS.md file. It applies to R packages that are being version controlled on GitHub. By incorporating a few simple and easy steps during the development process, you can ensure that versioning and updating of NEWS.md and DESCRIPTION is easily achieved for release.

Installation

The package can be installed from GitHub using the command

devtools::install_github("krlmlr/fledge")

Why use fledge?

Without {fledge}, you probably follow these steps at different stages of your workflow.

Check the previous version used, before assigning a new version number.
Manually update NEWS.md with each substantial change, and/or check the previous commit messages to decide what should go in the NEWS.md file.
Manually merge the NEWS.md files from different branches after reviewing the discrepancies.

{fledge} provides standardised version number updates to your package. It can also read your commit messages from recent commits and include the marked lines in NEWS.md. As the NEWS.md is generated by {fledge}, there is no need to merge it manually. All of this can be achieved with just one function call.

Using {fledge} would not only save you time, but will also streamline the process of versioning and updating NEWS.md.

Functions

{fledge} consists of the following functions that enable versioning at different stages through the package development lifecycle.

Function Name	Description	Stage Applicable
`bump_version(which)`	Increments the package version based on argument. (Version format supported major.minor.dev.patch)	Configuration, Development, Release
`finalize_version()`	Finalize the package version	Configuration, Development
`commit_version()`	Commits `NEWS.md` and `DESCRIPTION` to Git.	Release
`tag_version()`	Parses `NEWS.md` and creates/updates the tag for the most recent version.	Release
`update_news()`	Update `NEWS.md` with messages from top level commits	Used by `bump_version()`
`update_version()`	Update `NEWS.md` and `DESCRIPTION` with a new version	Used by `bump_version()`

Usage

The following sections show, how to combine these functions at different stages with any R package on GitHub. All {fledge} commands should be issued from the package directory of the target R package.

Initial Configuration

{fledge} assumes that the target R package is version-controlled with Git in a dedicated repository. The following steps are required to set up {fledge} for first time use, with your package.

Call bump_version() as given below to set the package version
```
fledge::bump_version()
```
Call finalize_version() as given below to update NEWS.md
```
fledge::finalize_version()
```

You are all set to switch to the development stage now. Ensure that you use bullet points (* or -) in your commit or merge messages to indicate the messages that you want to include in NEWS.md.

Development

{fledge} aims to update NEWS.md and DESCRIPTION correctly whenever a new version is assigned. In order to do this, the following steps need to be included throughout the development workflow.

In commit messages to master, mark everything that should go to NEWS.md with a bullet point (- or *). This is applicable to single commits, merge commits, or pull requests. Do not edit NEWS.md manually.
When you want to assign a version number to the current state of your R package, call
```
fledge::bump_version()
```
The default argument for bump_version is “dev”. So the dev part of the version number will be updated. It is good practice to assign a new version number before switching focus to another project.

Edit NEWS.md if required. Then call finalize_version() as below.

fledge::finalize_version()

This achieves the following:

 * `NEWS.md` is now composed, based on the most recent commit messages.
     To understand how `NEWS.md` is updated by fledge, see the section on `NEWS.md` implementation.
 * A new version number is assigned automatically (this is modeled after `usethis::use_version()`)
 * A tag matching the version number is assigned automatically, with the most recent `NEWS.md` messages included in the tag's message.

Releasing to CRAN

When you want to release your package to CRAN, follow the steps below:

Call bump_version() with the appropriate argument ("patch", "major", "minor"). e.g.,
```
fledge::bump_version("patch")
```
Edit NEWS.md, convert the “change log” to “release notes” – a higher-level description of features and bug fixes.
Call commit_version() as below
```
fledge::commit_version()
```
Make any necessary adjustments before releasing to CRAN.
Once the release/changes have been accepted by CRAN, use the following calls to tag the released version and to switch to a development version immediately.
```
fledge::tag_version()
fledge::bump_version()
```

Implementation

The following sections explain, how things actually work inside fledge

Updating `NEWS.md`

New entries are added to NEWS.md from commit messages to commits in master.

Only top-level commits are considered (roughly equivalent to git log --first-parent.) The messages from these commits are parsed. Only lines that start with a star * or a dash - are included.

If a line starts with three dashes, then everything past that line is excluded. Example: the following commit message

Merge f-fancy-feature to master, closes #5678

- Added fancy feature (#5678).

- Fixed bug as a side effect (#9012).

---

The fancy feature consists of the components:

- foo
- bar
- baz

will be added as below to NEWS.md:

- Added fancy feature (#5678).
- Fixed bug as a side effect (#9012).

When retrieving the current NEWS for defining the tag message, the entries between the first two first-level headers (starting with #) are returned. You can use second and third level headers and add as many empty lines as you want.

Collecting NEWS

The first function to call at any stage is always bump_version(). This does the following

Calls update_news() to collect NEWS entries from top-level commits.
Calls update_version() to increment the version in DESCRIPTION and add a header to NEWS.md.

Tagging for “dev” vs. other releases

bump_version() continues depending on the release type:

"dev" releases: Calls finalize_version() to commit DESCRIPTION and NEWS.md. Also creates a tag with a message. You can always edit NEWS.md and call finalize_version() again. Both the commit and the tag will be updated.
Other releases: Calls commit_version() to commit DESCRIPTION and NEWS.md without tagging. In this stage, you can edit NEWS.md and commit as much as you like. The tag is created only after you use tag_version() manually.

Caveats

If you rebase after creating a tag, you need to call finalize_version() to make sure the tag is moved to the mainline branch.

If you pushed after calling finalize_version() (directly or indirectly), the tag may have been pushed as well. In this case, invoke

git push origin :vx.y.z.9www

(where x.y.z.9www is the new version) to delete the newly created remote tag. This is the reason why {fledge} only tags "dev" releases automatically. Other releases always must be tagged manually with tag_version().