How to quickly find all git repos under a directory

Check out Dennis' answer in this post about find's -prune option:

How to use '-prune' option of 'find' in sh?

find . -name .git -type d -prune

Will speed things up a bit, as find won't descend into .git directories, but it still does descend into git repositories, looking for other .git folders. And that 'could' be a costly operation.

What would be cool is if there was some sort of find lookahead pruning mechanism, where if a folder has a subfolder called .git, then prune on that folder...

That said, I'm betting your bottleneck is in the network operation 'git pull', and not in the find command, as others have posted in the comments.

Here is an optimized solution:

#!/bin/bash
# Update all git directories below current directory or specified directory
# Skips directories that contain a file called .ignore

HIGHLIGHT="\e[01;34m"
NORMAL='\e[00m'

function update {
  local d="$1"
  if [ -d "$d" ]; then
    if [ -e "$d/.ignore" ]; then 
      echo -e "\n${HIGHLIGHT}Ignoring $d${NORMAL}"
    else
      cd $d > /dev/null
      if [ -d ".git" ]; then
        echo -e "\n${HIGHLIGHT}Updating `pwd`$NORMAL"
        git pull
      else
        scan *
      fi
      cd .. > /dev/null
    fi
  fi
  #echo "Exiting update: pwd=`pwd`"
}

function scan {
  #echo "`pwd`"
  for x in $*; do
    update "$x"
  done
}

if [ "$1" != "" ]; then cd $1 > /dev/null; fi
echo -e "${HIGHLIGHT}Scanning ${PWD}${NORMAL}"
scan *