git: Dynamically identify the "default" branch

This broadly assumes that the "default" remote is called "origin", but
that's better than assuming that plus the default branch name.

Thanks to https://joshtronic.com/2020/08/09/how-to-get-the-default-git-branch/

Suggested-by: Chris Lane <chris@chrislane.com>
Signed-off-by: Joe Groocock <me@frebib.net>

aliases

@@ -112,7 +112,7 @@ alias gitc='$EDITOR $XDG_CONFIG_HOME/git/config'
 alias ggignore='$EDITOR $XDG_CONFIG_HOME/git/gitignore'
 alias gcl="git clone --recursive"
 alias gco="git checkout"
-alias gcom="git checkout master"
+alias gcom="git checkout \"\$(git defbranch)\""
 alias ga="git add"
 alias gap="git add -p"
 alias gau="git add -u"
@@ -136,7 +136,7 @@ alias grba="grb --abort"
 alias grbc="grb --continue"
 alias grbsk="grb --skip"
 alias grbsh="grb --show-current"
-alias grbom="git rebase origin/master"
+alias grbom="git rebase \"origin/\$(git defbranch)\""
 gfrb() { remote="${1%/*}"; git fetch "$remote" && git rebase "$@"; }
 gfrbi() { remote="${1%/*}"; git fetch "$remote" && git rebase -i "$@"; }
 
@@ -160,7 +160,7 @@ alias gp="git push"
 alias gpf="gp --force"
 alias gpsu="git push --set-upstream"
 alias gpoH="git push origin HEAD"
-alias gpsuom="git push --set-upstream origin master"
+alias gpsuom="git push --set-upstream origin \"\$(git defbranch)\""
 alias gpall="git remote | xargs -L1 git push"
 alias gl="git pull --rebase"
 alias glp="gl && gp"

git/config

@@ -37,6 +37,7 @@
 	count = !echo $(pwd) && git rev-list HEAD --count
 	unpushed = !git log --oneline @{u}..HEAD
 	leaders = !git shortlog -s -n --all --no-merges
+	defbranch = !git symbolic-ref refs/remotes/origin/HEAD | sed \"s@^refs/remotes/origin/@@\"
 [advice]
 	statusHints = false
 	pushUpdateRejected = false