Update/build scripts: allow custom DLL names

Allow custom shared library names (eg, `git2-mycompany.dll` instead
of `git2-hash.dll`) to allow a single process to potentially load
multiple instances of libgit2.

Author: ethomson

UpdateLibgit2ToSha.ps1

@@ -6,7 +6,8 @@
 #>
 
 Param(
-    [string]$sha = 'HEAD'
+    [string]$sha = 'HEAD',
+    [string]$libgit2Name = ''
 )
 
 Set-StrictMode -Version Latest
@@ -83,7 +84,11 @@ Push-Location $libgit2Directory
 
     sc -Encoding ASCII (Join-Path $projectDirectory "nuget.package\libgit2\libgit2_hash.txt") $sha
 
-    $binaryFilename = "git2-" + $sha.Substring(0,7)
+    if (![string]::IsNullOrEmpty($libgit2Name)) {
+        $binaryFilename = $libgit2Name
+    } else {
+        $binaryFilename = "git2-" + $sha.Substring(0,7)
+    }
 
     $buildProperties = @"
 <?xml version="1.0" encoding="utf-8"?>

build.libgit2.ps1

@@ -11,6 +11,7 @@
 
 Param(
     [string]$vs = '10',
+    [string]$libgit2Name = '',
     [switch]$test,
     [switch]$debug
 )
@@ -23,7 +24,12 @@ $x86Directory = Join-Path $projectDirectory "nuget.package\libgit2\windows\x86"
 $x64Directory = Join-Path $projectDirectory "nuget.package\libgit2\windows\amd64"
 $hashFile = Join-Path $projectDirectory "nuget.package\libgit2\libgit2_hash.txt"
 $sha = Get-Content $hashFile 
-$binaryFilename = "git2-" + $sha.Substring(0,7)
+
+if (![string]::IsNullOrEmpty($libgit2Name)) {
+    $binaryFilename = $libgit2Name
+} else {
+    $binaryFilename = "git2-" + $sha.Substring(0,7)
+}
 
 $build_clar = 'OFF'
 if ($test.IsPresent) { $build_clar = 'ON' }