[DOC] Replace mentions of Gitter with Mattermost

CONTRIBUTING.md

@@ -24,14 +24,14 @@ Already know what you're looking for in this guide? Jump to the following sectio
 
 Don't know where to get started?
 Read [Joining the conversation](#joining-the-conversation) and pop into
-Gitter to introduce yourself! Let us know what your interests are and we
+Mattermost to introduce yourself! Let us know what your interests are and we
 will help you find an issue to contribute to. Thanks so much!
 
 ## Joining the conversation
 
 `tedana` is a young project maintained by a growing group of enthusiastic developers— and we're excited to have you join!
 Most of our discussions will take place on open [issues][link_issues].
-We also maintain a [gitter chat room][link_gitter] for more informal conversations and general project updates.
+We also maintain a [Mattermost chat room][link_mattermost] for more informal conversations and general project updates.
 
 There is significant cross-talk between these two spaces, and we look forward to hearing from you in either venue!
 As a reminder, we expect all contributions to `tedana` to adhere to our [code of conduct][link_coc].
@@ -347,7 +347,7 @@ You're awesome. :wave::smiley:
 [link_issues]: https://github.com/ME-ICA/tedana/issues
 [link_milestones]: https://github.com/ME-ICA/tedana/milestones/
 [link_project_boards]: https://github.com/ME-ICA/tedana/projects
-[link_gitter]: https://gitter.im/me-ica/tedana
+[link_mattermost]: https://mattermost.brainhack.org/brainhack/channels/tedana
 [link_coc]: https://github.com/ME-ICA/tedana/blob/main/CODE_OF_CONDUCT.md
 [link_stale-bot]: https://github.com/probot/stale
 

README.md

@@ -10,7 +10,7 @@
 [![Codecov](https://codecov.io/gh/me-ica/tedana/branch/main/graph/badge.svg)](https://codecov.io/gh/me-ica/tedana)
 [![Average time to resolve an issue](http://isitmaintained.com/badge/resolution/ME-ICA/tedana.svg)](http://isitmaintained.com/project/ME-ICA/tedana "Average time to resolve an issue")
 [![Percentage of issues still open](http://isitmaintained.com/badge/open/ME-ICA/tedana.svg)](http://isitmaintained.com/project/ME-ICA/tedana "Percentage of issues still open")
-[![Join the chat at https://gitter.im/ME-ICA/tedana](https://badges.gitter.im/ME-ICA/tedana.svg)](https://gitter.im/ME-ICA/tedana?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Join the chat on Mattermost](https://img.shields.io/badge/Chat%20on-Mattermost-purple.svg)](https://mattermost.brainhack.org/brainhack/channels/tedana)
 [![Join our tinyletter mailing list](https://img.shields.io/badge/receive-our%20newsletter%20❤%EF%B8%8F-blueviolet.svg)](https://tinyletter.com/tedana-devs)
 [![All Contributors](https://img.shields.io/badge/all_contributors-20-orange.svg?style=flat-square)](#contributors)
 [![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
@@ -118,13 +118,13 @@ Want to learn more about our plans for developing ``tedana``?
 Have a question, comment, or suggestion?
 Open or comment on one of [our issues](https://github.com/ME-ICA/tedana/issues)!
 
-If you're not sure where to begin, feel free to pop into [Gitter](https://gitter.im/ME-ICA/tedana) and introduce yourself!
+If you're not sure where to begin, feel free to pop into [Mattermost](https://mattermost.brainhack.org/brainhack/channels/tedana) and introduce yourself!
 We will be happy to help you find somewhere to get started.
 
 If you don't want to get lots of notifications, we send out newsletters approximately once per month though our TinyLetter mailing list.
 You can view the [previous newsletters](https://tinyletter.com/tedana-devs/archive) and/or sign up to receive future ones at [https://tinyletter.com/tedana-devs](https://tinyletter.com/tedana-devs).
 
-We ask that all contributors to ``tedana`` across all project-related spaces (including but not limited to: GitHub, Gitter, and project emails), adhere to our [code of conduct](https://github.com/ME-ICA/tedana/blob/main/CODE_OF_CONDUCT.md).
+We ask that all contributors to ``tedana`` across all project-related spaces (including but not limited to: GitHub, Mattermost, and project emails), adhere to our [code of conduct](https://github.com/ME-ICA/tedana/blob/main/CODE_OF_CONDUCT.md).
 
 ## Contributors
 

docs/index.rst

@@ -44,8 +44,8 @@ tedana: TE Dependent ANAlysis
    :target: http://isitmaintained.com/project/ME-ICA/tedana
    :alt: Percentage of issues still open
 
-.. image:: https://badges.gitter.im/ME-ICA/tedana.svg
-   :target: https://gitter.im/ME-ICA/tedana
+.. image:: https://img.shields.io/badge/Chat%20on-Mattermost-purple.svg
+   :target: https://mattermost.brainhack.org/brainhack/channels/tedana
    :alt: Join the chat
 
 .. image:: https://img.shields.io/badge/receive-our%20newsletter%20❤%EF%B8%8F-blueviolet.svg

docs/support.rst

@@ -27,10 +27,9 @@ There are multiple mechanisms for development-related communication, which can l
 Here we attempt to clarify when and how each communication pathway should be used:
 
 - GitHub Issues and Pull Requests: Issues and PRs should be the **main avenue of communication** for questions and proposals related to tedana's development.
-- Gitter: While tedana does have a Gitter channel, this channel should not be used for discussions. Instead, its primary use is to redirect to **existing** Issues and PRs, whether open or closed.
 - Monthly Newsletter: The `monthly newsletter`_ is used to make announcements from the tedana developers to the tedana users. Discussions that start in Issues or PRs may move to the newsletter if they are news-worthy.
 - NeuroStars: The NeuroStars forum is to be used by tedana users to ask questions about how to use tedana. tedana's developers may answer usage questions on NeuroStars, but development-related discussions should happen in GitHub Issues and PRs.
-- Mattermost: There is a `tedana channel in the BrainHack Mattermost`_. This is primarily used for online discussions during BrainHack-related hackathons (for example, the annual OHBM hackathon), if and when there is a tedana-related project. **This channel is not regularly monitored by tedana developers** and should not be used outside of hackathons.
+- Mattermost: There is a `tedana channel in the BrainHack Mattermost`_. This is primarily used for online discussions during BrainHack-related hackathons (for example, the annual OHBM hackathon), if and when there is a tedana-related project. We also use this channel to redirect to **existing** Issues and PRs, whether open or closed.
 
 .. _monthly newsletter: https://github.com/ME-ICA/newsletters
 .. _tedana channel in the BrainHack Mattermost: https://mattermost.brainhack.org/brainhack/channels/tedana