git-stack-tree

#!/bin/bash
# git-stack-tree: print a visual representation of the current branch stack

MAIN_BRANCH=$(git config init.defaultBranch 2>/dev/null || echo "main")
CURRENT=$(git branch --show-current 2>/dev/null || echo "")

find_child() {
    local target="$1"
    while read -r key value; do
        local branch="${key#branch.}"
        branch="${branch%.stack-parent}"
        if [ "$value" = "$target" ]; then
            echo "$branch"
            return
        fi
    done < <(git config --get-regexp '^branch\..*\.stack-parent$' 2>/dev/null)
}

# walk down from current branch to find the bottom of the stack
BOTTOM=""
if [ -n "$CURRENT" ] && [ "$CURRENT" != "$MAIN_BRANCH" ]; then
    B="$CURRENT"
    while true; do
        BOTTOM="$B"
        PARENT=$(git config "branch.$B.stack-parent" 2>/dev/null || echo "")
        if [ -z "$PARENT" ] || [ "$PARENT" = "origin/$MAIN_BRANCH" ] || [ "$PARENT" = "$MAIN_BRANCH" ]; then
            break
        fi
        B="$PARENT"
    done
else
    BOTTOM=$(find_child "origin/$MAIN_BRANCH")
    if [ -z "$BOTTOM" ]; then
        BOTTOM=$(find_child "$MAIN_BRANCH")
    fi
fi

# walk up from bottom collecting the full stack
STACK=()
if [ -n "$BOTTOM" ]; then
    B="$BOTTOM"
    while [ -n "$B" ]; do
        STACK+=("$B")
        B=$(find_child "$B")
    done
fi

# print the tree
MAIN_LINE="$MAIN_BRANCH"
if [ "$CURRENT" = "$MAIN_BRANCH" ]; then
    MAIN_LINE="$MAIN_LINE ←"
fi
echo "$MAIN_LINE"
INDENT=" "
for (( i=0; i<${#STACK[@]}; i++ )); do
    BRANCH="${STACK[$i]}"
    PARENT=$(git config "branch.$BRANCH.stack-parent" 2>/dev/null || echo "origin/$MAIN_BRANCH")

    # count commits between parent and branch
    COMMITS=$(git log --oneline "$PARENT..$BRANCH" 2>/dev/null | wc -l | tr -d ' ')

    LINE="${INDENT}└─ ${BRANCH}"
    if [ "$COMMITS" -gt 0 ]; then
        LINE="$LINE [$COMMITS]"
    fi
    if [ "$BRANCH" = "$CURRENT" ]; then
        LINE="$LINE ←"
    fi
    echo "$LINE"
    INDENT="$INDENT    "
done