utilities/pipelines/publish/helper/Get-ModuleVersionChange.ps1

<#
.SYNOPSIS
Get current and previous major and minor version, if different.

.DESCRIPTION
Get current and previous major and minor version, if different.
Retrieves target Major.Minor from module version.json and compares with values from the previous git head.

.PARAMETER VersionFilePath
Mandatory. Path to the module version.json file.

.EXAMPLE
# Note: "version" value is "0.1" and was not updated in the last commit
Get-ModuleVersionChange -VersionFilePath 'C:\avm\res\key-vault\vault\version.json'

Returns null

.EXAMPLE
# Note:"version" value is updated from "0.1" to "0.2" in the last commit
Get-ModuleVersionChange -VersionFilePath 'C:\avm\res\key-vault\vault\version.json'

Name                           Value
----                           -----
oldVersion                     0.1
newVersion                     0.2

#>
function Get-ModuleVersionChange {

    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [string] $VersionFilePath
    )

    $diff = git diff --diff-filter=AM HEAD^ HEAD $VersionFilePath | Out-String

    if ($diff -match '\-\s*"version":\s*"([0-9]{1})\.([0-9]{1})".*') {
        $oldVersion = (New-Object System.Version($matches[1], $matches[2]))
    }

    if ($diff -match '\+\s*"version":\s*"([0-9]{1})\.([0-9]{1})".*') {
        $newVersion = (New-Object System.Version($matches[1], $matches[2]))
    }

    if ($newVersion -lt $oldVersion) {
        Write-Verbose 'The new version is smaller than the old version'
    } elseif ($newVersion -eq $oldVersion) {
        Write-Verbose 'The new version equals the old version'
    } else {
        Write-Verbose 'The new version is greater than the old version'
    }

    if (-not [String]::IsNullOrEmpty($newVersion) -and -not [String]::IsNullOrEmpty($oldVersion)) {
        return @{
            newVersion = $newVersion
            oldVersion = $oldVersion
        }
    }
}