Functions/New-GitBranch.ps1

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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

function New-GitBranch
{
    <#
    .SYNOPSIS
 
    Creates a new branch in a Git repository.
 
    .DESCRIPTION
 
    The `New-GitBranch` creates a new branch in a Git repository and then switches to (i.e. checks out) that branch.
 
    It defaults to the current repository. Use the `RepoRoot` parameter to specify an explicit path to another repo.
 
    This function implements the `git branch <branchname> <startpoint>` and `git checkout <branchname>` commands.
 
    .EXAMPLE
 
    New-GitBranch -RepoRoot 'C:\Projects\LibGit2' -Name 'develop'
 
    Demonstrates how to create a new branch named 'develop' in the specified repository.
 
    .EXAMPLE
 
    New-GitBranch -Name 'develop
 
    Demonstrates how to create a new branch named 'develop' in the current directory.
    #>

    [CmdletBinding()]
    param(
        [string]
        # Specifies which git repository to add a branch to. Defaults to the current directory.
        $RepoRoot = (Get-Location).ProviderPath,

        [Parameter(Mandatory=$true)]
        [string]
        # The name of the new branch.
        $Name,

        [string]
        # The revision where the branch should be started/created. A revision can be a specific commit ID/sha (short or long), branch name, tag name, etc. Run git help gitrevisions or go to https://git-scm.com/docs/gitrevisions for full documentation on Git's revision syntax.
        $Revision = "HEAD"
    )

    Set-StrictMode -Version 'Latest'

    $repo = Find-GitRepository -Path $RepoRoot -Verify
    if( -not $repo )
    {
        return
    }

    try
    {
        if( Test-GitBranch -RepoRoot $RepoRoot -Name $Name )
        {
            Write-Warning ('Branch {0} already exists in repository {1}' -f $Name, $RepoRoot)
            return
        }

        $newBranch = $repo.Branches.Add($Name, $Revision)
        $checkoutOptions = New-Object LibGit2Sharp.CheckoutOptions
        $repo.Checkout($newBranch, $checkoutOptions)
    }
    catch [LibGit2Sharp.LibGit2SharpException]
    {
        Write-Error ("Could not create branch '{0}' from invalid starting point: '{1}'" -f $Name, $Revision)
    }
    finally
    {
        $repo.Dispose()
    }
}