Add configuration for git

- Add .config/git/config
  + Define aliases
  + Configure default behavior in various situations
  + Add user information with signing key
- Add .config/git/commit_msg_template.txt
- Add .config/git/ignore
- Integrate `git` aliases into the shell

.config/shell/aliases

@@ -5,3 +5,105 @@
 
 # Manage the bare `git` repository in ~/ holding the dotfiles
 alias dotfiles='git --git-dir=$XDG_DATA_HOME/dotfiles --work-tree=$HOME'
+
+
+# Integrate `git`
+if _command_exists git; then
+
+    # Check if a "main" branch exists in place of a "master" branch
+    git_main_branch() {
+        if [ -n "$(git branch --list main)" ]; then
+           echo "main"
+        else
+           echo "master"
+        fi
+    }
+
+    alias g='git'
+
+    alias ga='git add'
+    alias gap='git add --patch'
+
+    alias gbr='git branch'
+    alias gbra='git branch --all'
+    alias gbrd='git branch --delete'
+    alias gbrdd='git branch --delete --force'
+    alias gbrm='git branch --move'
+
+    alias gci='git commit'
+    alias gcim='git commit --message'
+
+    alias gcl='git clone'
+
+    alias gco='git checkout'
+    alias gcob='git checkout -b'
+    alias gcod='git checkout develop'
+    alias gcom='git checkout $(git_main_branch)'
+
+    alias gcp='git cherry-pick'
+
+    alias gdf='git diff-minimal'
+    alias gdlc='git diff-last-commit'
+    alias gds='git diff-staged'
+
+    alias gfe='git fetch'
+
+    alias ghi='git history'
+    alias ghia='git history --all'
+
+    alias glc='git last-commit'
+
+    alias glg='git log'
+    alias glga='git log --all'
+
+    alias gme='git merge'
+    alias gmea='git merge --abort'
+    alias gmec='git merge --continue'
+    alias gmeff='git merge --ff-only'
+    alias gmenoff='git merge --no-ff'
+
+    alias gol='git oneline'
+    alias gola='git oneline --all'
+
+    alias gpl='git pull'
+    alias gplrb='git pull --rebase'
+
+    alias gps='git push'
+    alias gpsf='git push --force'
+
+    alias grb='git rebase --committer-date-is-author-date'
+    alias grba='git rebase --abort'
+    alias grbc='git rebase --continue'
+    alias grbi='git rebase --interactive'
+    alias grbq='git rebase --quit'
+    alias grbs='git rebase --skip'
+
+    alias grepc='git grep-code'
+    alias grepl='git grep-log'
+    alias grept='git grep-text'
+
+    alias grl='git reflog'
+
+    alias grm='git rm'
+
+    alias grs='git reset'
+
+    alias grv='git revert'
+
+    alias gs='git status'
+    alias gss='git status --short'
+
+    alias gsh='git show'
+
+    alias gst='git stash'
+    alias gsta='git stash push --include-untracked'
+    alias gstam='git stash push --include-untracked --message'
+    alias gstapp='git stash apply'
+    alias gstl='git stash list'
+    alias gstp='git stash pop'
+    alias gstsh='git stash show'
+
+    alias gsu='git summary'
+    alias gsua='git summary --all'
+
+fi