Differences

This shows you the differences between two versions of the page.

--- en:git:git-subtree [2012/01/14 08:38]
alex
+++ en:git:git-subtree [2012/08/27 09:42] (current)
alex
@@ Line 1: / Line 1: @@
 ====== git-subtree ======
-Sometimes projects can have complex relationships.  Perhaps a project develops a utility or libary internally that ends up becoming its own separate project.  Perhaps a project uses a particular library, but adds some features to it in their own repository.  How are these commits reconciled?  One method is the use of the script [[github.com/apenwarr/git-subtree|git-subtree]].  It is a very handy tool that allows for a repository to be associated with a directory or subtree of a different repository, yet allow for bi-directional transfer of commits.  In Arch Linux, git-subtree is in the AUR as ''git-subtree-git'' so it can be installed with yaourt with ''yaourt -S git-subtree-git''.
+Sometimes projects can have complex relationships.  Perhaps a project develops a utility or libary internally that ends up becoming its own separate project.  Perhaps a project uses a particular library, but adds some features to it in their own repository.  How are these commits reconciled?  One method is the use of the script [[http://github.com/apenwarr/git-subtree|git-subtree]].  It is a very handy tool that allows for a repository to be associated with a directory or subtree of a different repository, yet allow for bi-directional transfer of commits.  In Arch Linux, git-subtree is in the AUR as ''git-subtree-git'' so it can be installed with yaourt with ''yaourt -S git-subtree-git''.
 Some time ago, I started working on a project that involved using XBee ZigBee radios from Digi.  Unfortunately, the software provided is windows-only and is lacking some very important features, like packet generation and decoding.  As a part of the project, I worked on a cross-platform open source re-implementation of a ZigBee terminal that can talk to the XBee radios in packet mode and create and decode packets with a nice interface.  The application evolved to the point where it would be nice to split it off into its own repository.  So, I installed git-subtree and went to work.  Or not.  The documentation is really bad if you're not a git expert.  After consulting the oracle of google, I discovered a very good [[http://psionides.eu/2010/02/04/sharing-code-between-projects-with-git-subtree/|blog post]] on the matter.  Please see the link for the details as Jakub does a much better job of explaining it than myself.
@@ Line 83: / Line 83: @@
 Slick.  Now that that's taken care of, time to get back to the real engineering...
+===== Helper Script =====
+As I have been using the commands listed here quite often, I decided to put together a helper script for managing these subtrees.  Take the script below, modify it to match your repository configuration, and include it in your repository alongside the subtree.  Then you can call it with no arguments or with a single argument of 'pull' to pull from the remote subtree repository, or add 'push' to push to the remote subtree repository.  As is, the script performs the exact commands listed in the above section, aside from the splitting off of the subdirectory in the process of creating a separate repository.
+<code sh>
+#!/bin/bash
+# Git subtree manager
+# Alex Forencich <alex@alexforencich.com>
+# This script facilitates easy management of subtrees
+# included in larger repositories as this script can
+# be included in the repository itself.
+# Note:
+# Requires git-subtree
+# https://github.com/apenwarr/git-subtree
+# Settings
+# uncomment to use --squash
+#squash="yes"
+# Remote repository
+repo="git@github.com:alexforencich/zigbee-terminal.git"
+# Remote name
+remote="zbt"
+# Subdirectory to store code in
+subdir="zigbee-terminal"
+# Remote branch
+branch="master"
+# Backport branch name (only used for pushing)
+backportbranch="${remote}backport"
+# Add commit message
+addmsg="added ${subdir} as a subproject"
+# Merge commit message
+mergemsg="merged changes in ${subdir}"
+# Usage
+# add - adds subtree
+# pull - default, pulls from remote
+# push - pushes to remote
+squashflag=""
+if [ $squash ]; then
+  squashflag="--squash"
+fi
+action="pull"
+cd $(git rev-parse --show-toplevel)
+if [ ! -d "$subdir" ]; then
+    action="add"
+fi
+if [ -n "$1" ]; then
+    action="$1"
+fi
+# array contains value
+# usage: contains array value
+function contains() {
+    local n=$#
+    local value=${!n}
+    for ((i=1;i < $n;i++)) {
+        if [ "${!i}" == "${value}" ]; then
+            echo "y"
+            return 0
+        fi
+    }
+    echo "n"
+    return 1
+}
+case "$action" in
+  add)
+    if [ $(contains $(git remote) "$remote") != "y" ]; then
+      git remote add "$remote" "$repo"
+    fi
+    git fetch "$remote"
+    git subtree add -P "$subdir" $squashflag -m "$addmsg" "$remote/$branch"
+    ;;
+  pull)
+    if [ $(contains $(git remote) "$remote") != "y" ]; then
+      git remote add "$remote" "$repo"
+    fi
+    git fetch "$remote"
+    git subtree merge -P "$subdir" $squashflag -m "$mergemsg" "$remote/$branch"
+    ;;
+  push)
+    if [ $(contains $(git remote) "$remote") != "y" ]; then
+      git remote add "$remote" "$repo"
+    fi
+    git subtree split -P "$subdir" -b "$backportbranch"
+    git push "$remote" "$backportbranch:$branch"
+    ;;
+  *)
+    echo "Error: unknown action!"
+    exit 1
+esac
+exit 0
+</code>