Partial Clean Install with Maven after Git Merge/Pull

Since you can detect the list of pom.xml changes between two commits:

git diff --name-status <commit1> <commit2>

(see also "Detail change after Git pull")

, you can make a script which would, for each module, do a mvn clean install.

Thanks to VonC's answer, I have completed a script that does what I desired.

The project is a POM Project that contains sub-POM Projects that house the main projects for the application. I achieved the desired result by getting the current working branch to call git diff --name-status HEAD@{1} <current_branch>.

This got the list of the changed files within the project, which I then split into an array. Unfortunately I could not get the split to work well, so the array is organized as change type followed by file path.

Then I checked string size, skipping single character strings. The next step was to split the string into an array, delimited by /. Checked if it exists in an array if root paths, adding if it does not.

Lastly, loop over the root path array and do the maven calls.

################################################################################
#
# License:.....GNU General Public License v3.0
# Author:......CodeMonkey
# Date:........14 November 2018
# Title:.......GitMavenCleanInstall.sh
# Description: This script is designed to cd to a set Maven POM Project,
#   perform a git remote update and pull, and clean install the changed
#   files projects.
# Notice:......The project structure this script was originally set to target
#   is structured as a Maven POM Project that contains several sub-POM Projects.
#   The sub-POM Projects contain Maven Java Application projects. The targets
#   should be easy to change, and allow for others to target other structures.
#
################################################################################
#
# Change History: N/A
#
################################################################################

#!/bin/bash
#Function to check if array has element
containsElement () {
    local e match="$1"
    shift
    for e; do [[ "$e" == "$match" ]] && return 0; done
    return 1
}

#Navigate to the POM Project
cd PATH/TO/POM/PROJECT
#Remote update
git remote update -p
#Pull
git pull

#Get the current working branch
CURRENT_BRANCH="$(git branch | sed -n -e 's/^\* \(.*\)/\1/p')"
#Get the output of the command git diff
GIT_DIFF_OUTPUT="$(git diff --name-status HEAD@{1} ${CURRENT_BRANCH})"

#Split the diff output into an array
read =a GIT_DIFF_OUTPUT_ARY <<< $GIT_DIF_OUTPUT
#Declare empty array for root path
declare -a GIT_DIFF_OUTPUT_ARY_ROOT_PATH=()
FORWARD='/'
#Loop diff output array
for i in "$GIT_DIFF_OUTPUT_ARY[@]}"
do
    #Check that the string is not 1 Character
    if [[ "$(echo -n $1 | wc -m)" != 1 ]]
    then
        #Split the file path by /
        IFS='/' read -ra SPLIT <<< $i
        #Concatenate first path + / + second path
        path=${SPLIT[0]}$FORWARD${SPLIT[1]}
        #Call function to see if it already exists in the root path array
        containsElement "$path" "${GIT_DIFF_OUTPUT_ARY_ROOT_PATH[@]}"
        if [[ $? != 0 ]]
        then
            #Add the path since it was not found
            GIT_DIFF_OUTPUT_ARY_ROOT_PATH+=($path)
        fi
    fi
done

#Loop root path array
for val in ${GIT_DIFF_OUTPUT_ARY_ROOT_PATH[@]}
do
    #CD into root path
    cd $val
    #Maven call to clean install
    mvn -DskipTests=true --errors -T 8 -e clean install
    #CD back up before next project
    cd ../../
done