A utility library that includes a wrapper for imlib2

http://www.linuxbrit.co.uk/giblib/

Tools and library routines for working with GIF images

https://sourceforge.net/projects/giflib/

Manipulates GIF images and animations

http://www.lcdf.org/gifsicle/

Frontend to easily manage filesystem connections

https://docs.xfce.org/apps/gigolo/start

GNU Image Manipulation Program

https://www.gimp.org/

GutenPrint Printer Driver

http://gimp-print.sourceforge.net/

C source code reformatter

http://www.gnu.org/software/indent/indent.html

GIO bindings not available in gtk-sharp

http://github.com/mono/gio-sharp

Distributed source code management tool

https://git-scm.com/

Git command for automating fixup/autosquash commits

https://github.com/tummychow/git-absorb

Distributed, offline-first bug tracker embedded in git, with bridges

https://github.com/MichaelMure/git-bug

Git remote helper to interact with Mercurial repositories

https://github.com/glandium/git-cinnabar

Command-line tool for working with Gerrit

https://godoc.org/golang.org/x/review/git-codereview

Sleek and powerful Git GUI

https://git-cola.github.io/

CVS emulation and import/export for git

https://git-scm.com/

Syntax-highlighting pager for git/diff

https://github.com/dandavison/delta

Sub-commands for repo summary, repl, changelog population, and more

https://github.com/tj/git-extras/

git filter-repo is a versatile tool for rewriting history

https://github.com/newren/git-filter-repo

Git GUI (Graphical User Interface) components

https://git-scm.com/

Git extension for versioning large files

https://git-lfs.github.com/

Git "merge" driver for GNU style ChangeLog files

https://www.gnu.org/software/vc-changelog/

GNU Emacs modes for Git-related files

https://github.com/magit/git-modes

Import from and submit to Perforce repositories using git

https://git-scm.com/

Git commands for navigating and editing Git commit history

https://github.com/ridiculousfish/git-prev-next

Git command for managing subrepositories

https://github.com/ingydotnet/git-subrepo

Bidirectional operation between a Subversion repository and Git

https://git-scm.com/

Util to keep branches in sync with remotes in git

https://github.com/ctubbsii/git-sync

Assorted git-related scripts and tools

https://github.com/MestreLion/git-tools

Compact self-hosted Git service

https://gitea.io/en-US/

GTK-based git repository viewer

https://wiki.gnome.org/Apps/Gitg

GitHub Enterprise Backup Utilities

https://github.com/github/backup-utils

Access control layer on top of git

https://github.com/sitaramc/gitolite

Access control layer on top of git

https://github.com/sitaramc/gitolite/tree/g2

Graphical interface to git repositories

https://francescmm.github.io/GitQlient/

Smart terminal helper for git projects

https://github.com/muesli/gitty

GNOME Javascript binding

http://live.gnome.org/Gjs

Graphical frontend to su

http://www.gnu.org/non-gnu/gksu/

Program to create labels and business cards

http://snaught.com/glabels/

User interface builder for GTK+ 3

https://glade.gnome.org/

Eclipse Jakarta EE Platform

https://projects.eclipse.org/projects/ee4j.glassfish

Reference implementation of the Java EE application server

https://glassfish.java.net/

OpenGL spinning pocket watch demo and benchmark utility

GL Tubing and Extrusion Library

https://linas.org/gle/

OpenGL Extension Wrangler Library

http://glew.sourceforge.net/

Network-related giomodules for glib

Some useful routines of C programming (current stable version)

https://www.gtk.org/

C++ interfaces for glib2

https://www.gtkmm.org/

OpenGL image compositing library

http://freedesktop.org/Software/glitz

C++ mathematics library for software based on the OpenGL GLSL

https://glm.g-truc.net/

Library of C++ classes for flexible logging

https://github.com/google/glog