tdiff (Transitive Diff)

This is still under development.

For applications that live in shared Git repositories, it can be difficult to determine which changes between two Git commits are relevant to the application and which are not.

tdiff aims to isolate only the relevant changes for an application and report those changes in various formats.

Relative changes are determined by building a graph of package dependencies and ignoring packages not reachable from a given package.

To illustrate, consider the following set of 6 Go packages:

myorg/app_one
    imports myorg/lib/collections
    imports thirdparty/http_util

myorg/app_two
    imports myorg/format/text

myorg/lib/collections
    imports myorg/format/text
    imports net/http

myorg/format/text

thirdparty/http_util
    imports net/http

net/http

There relevant set of packages for each:

• myorg/app_one: [myorg/app_one, myorg/lib/collections, thirdparty/http_util, myorg/format/text, net/http]
• myorg/app_two: [myorg/app_two, myorg/format/text]
• myorg/lib/collections: [myorg/lib/collections, myorg/format/text, net/http]
• myorg/format/text: [myorg/format/text]
• thirdparty/http_util: [thirdparty/http_util, net/http]
• net/http: [net/http]

Given that, when determining changes for myorg/app_two, only changes in the myorg/app_two and myorg/format/text packages are considered.

Installing

go get -u github.com/alecholmes/tdiff

Uses

"Related" means the package passed to tdiff and all recursively reachable packages.

List related packages changed after the given SHA

tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -packages

List related files changed after the given SHA

tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -files

List Git commits after the given SHA that contain changes to related files

tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -commits

Get JSON output for all of the above, and more

tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -json

The JSON output includes separate sections for packages, files, and commits.

Additionally, each changed package also includes a path indicating how it is reachable from the given root path. A path of ["A", "B", "C"] indicates "A imports B, and B imports C".

HTML Summary

# This will print the name of the summary HTML temp file:
tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -html

# Open the summary HTML file:
open $(tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -html)

Including Non-Go Files

tdiff can consider and include all files, not just Go source files. This is useful for picking up changes to config files, for example.

To include all files, add the -artifacts flag, e.g. tdiff -package your/app/list_utils -sha OLDER_GIT_SHA -packages -artifacts.

Notes

If a package is changed after the given SHA and before being added as a dependency, and does not change after this, irrelevant changes will be included.

Roadmap

• Better usage/help output.
• Nice error messages.
• Check that git and go tool are installed.
• Flag for verbose output (IN PROGRESS).
• Better unit test coverage, especially for the app package.
• Investigate: Enumerate potential edge cases.
  • Could internal or test packages cause problems?
• Investigate: Use kingpin instead of flag library?

License

This source code is open source through the GNU Lesser General Public License v3.0. See the LICENSE file for full details or this helpful summary.