While Mercurial has a well defined (albeit internal) API that can be used to write extensions that extend the functionality of Mercurial, git’s extension model follows the Unix philosophy of composing small, simple programs to achieve a similar effect. What that means is that git “extensions” can be written in any language and by following a few simple rules it’s still possible to add commands that appear as if they were built-in. Example: git activity To see the activity on all the branches in a repository I’ve implemented a git activity command. git activity shows the latest commit on every branch, sorted by recency. It shows the following output when executed in the Rails repository: The script is written in bash and fairly straightforward. We set up colours and parse some command line options the scripts supports (e.g. to turn off colours, to limit the output) and then run git for-each-ref to output information about each ref. #!/bin/bash set -e GIT_OPTS="" OUTPUT_FILTER="cat" # no-op commit_id_format=$(tput setaf 1) date_format=$(tput bold; tput setaf 4) author_format=$(tput setaf 2) ref_name_format=$(tput setaf 3) bold=$(tput bold) reset=$(tput sgr0) function usage() { echo "" echo "git activity" echo "" echo " See 'man git-activity' for further information" } # actually parse the options and do stuff while [[ $1 = -?* ]]; do case $1 in -h|--help) usage exit 0 ;; --fetch) echo "Fetch updates" git fetch -q ;; -c|--count) shift limit=${1-"10"} #OUTPUT_FILTER="tail -n ${limit}" GIT_OPTS="--count=${limit}" ;; --no-color|--no-colour) commit_id_format="" date_format="" author_format="" ref_name_format="" bold="" reset="" ;; *) ;; esac shift done # Use newline as a field separator IFS=$(echo -en "\n\b") # Use tac if available, otherwise tail with the possibly-not-always-available # -r flag (for reverse output) TAC=$(which tac || echo 'tail -r') for line in $(git for-each-ref ${GIT_OPTS} refs/remotes --format="%(authordate:relative)|%(objectname:short)|%(authorname)|%(refname:short)|%(subject)" --sort="-authordate"); do fields=(`echo $line | tr "|" "\n"`) printf "${date_format}%15s${reset} ${commit_id_format}%s${reset} - ${author_format}[%s]${reset} (${ref_name_format}%s${reset}): %s\n" ${fields[*]} done | eval $TAC # reverse sort the output to show the newest entry last The important rules to follow to make this script available as a git sub-command are: It should be named git-COMMANDNAME, in this case it’s called git-activity and it needs to be executable [...]
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