Sync eng/common directory with azure-sdk-tools repository (#60)

eng/common/scripts/SemVer.ps1

@@ -0,0 +1,78 @@
+<#
+.DESCRIPTION
+Parses a semver version string into its components and supports operations around it.
+Example: 1.2.3-preview.4
+Components: Major.Minor.Patch-PrereleaseLabel.PrereleaseNumber
+#>
+
+class SemVer {
+    [int] $Major
+    [int] $Minor
+    [int] $Patch
+    [string] $PrereleaseLabel
+    [int] $PrereleaseNumber
+    [bool] $IsPrerelease
+    [string] $RawVersion
+
+    SemVer(
+        [string] $versionString
+    ){
+        # Regex inspired but simplifie from https://semver.org/#is-there-a-suggested-regular-expression-regex-to-check-a-semver-string
+        $SEMVER_REGEX = "^(?<major>0|[1-9]\d*)\.(?<minor>0|[1-9]\d*)\.(?<patch>0|[1-9]\d*)(?:-?(?<prelabel>[a-zA-Z-]*)(?:\.?(?<prenumber>0|[1-9]\d*)))?$"
+        
+        if ($versionString -match $SEMVER_REGEX) {
+            if ($null -eq $matches['prelabel']) {
+                # artifically provide these values for non-prereleases to enable easy sorting of them later than prereleases.
+                $prelabel = "zzz"
+                $prenumber = 999;
+                $isPre = $false;
+            }
+            else {
+                $prelabel = $matches["prelabel"]
+                $prenumber = [int]$matches["prenumber"]
+                $isPre = $true;
+            }
+
+            
+            $this.Major = [int]$matches.Major
+            $this.Minor = [int]$matches.Minor
+            $this.Patch = [int]$matches.Patch
+            $this.PrereleaseLabel = $prelabel
+            $this.PrereleaseNumber = $prenumber
+            $this.IsPrerelease = $isPre
+            $this.RawVersion = $versionString
+        }      
+        else
+        {
+            throw "Invalid version string: $versionString"
+        }
+    }
+
+    [string] ToString(){
+        if ($this.IsPrerelease -eq $false)
+        {
+            $versionString = "{0}.{1}.{2}" -F $this.Major, $this.Minor, $this.Patch
+        }
+        else
+        {
+            $versionString = "{0}.{1}.{2}-{3}.{4}" -F $this.Major, $this.Minor, $this.Patch, $this.PrereleaseLabel, $this.PrereleaseNumber
+        }
+        return $versionString;
+    }    
+
+    
+    [void] IncrementAndSetToPrerelease(){
+        if  ($this.IsPrerelease -eq $false)
+        {
+            $this.PrereleaseLabel = 'preview'
+            $this.PrereleaseNumber = 1
+            $this.Minor++
+            $this.Patch = 0
+            $this.IsPrerelease = $true
+        }
+        else
+        {
+            $this.PrereleaseNumber++
+        }
+    }
+}