feat(cli): add --var shorthand for --variable (#8710)

`--variable` is used frequently enough to deserve a shorthand. Unfortunately,
`-v` is taken by verbose, and `-V` is too easily confused with version or
verbose, so we're left with "--var".

cli/templatecreate.go

@@ -170,6 +170,11 @@ func (r *RootCmd) templateCreate() *clibase.Cmd {
 			Description: "Specify a set of values for Terraform-managed variables.",
 			Value:       clibase.StringArrayOf(&variables),
 		},
+		{
+			Flag:        "var",
+			Description: "Alias of --variable.",
+			Value:       clibase.StringArrayOf(&variables),
+		},
 		{
 			Flag:        "provisioner-tag",
 			Description: "Specify a set of tags to target provisioner daemons.",

cli/templatepush.go

@@ -291,6 +291,11 @@ func (r *RootCmd) templatePush() *clibase.Cmd {
 			Description: "Specify a set of values for Terraform-managed variables.",
 			Value:       clibase.StringArrayOf(&variables),
 		},
+		{
+			Flag:        "var",
+			Description: "Alias of --variable.",
+			Value:       clibase.StringArrayOf(&variables),
+		},
 		{
 			Flag:        "provisioner-tag",
 			Description: "Specify a set of tags to target provisioner daemons.",

cli/testdata/coder_templates_create_--help.golden

@@ -34,6 +34,9 @@ Create a template from the current directory or as specified by flag
       --provisioner-tag string-array
           Specify a set of tags to target provisioner daemons.
 
+      --var string-array
+          Alias of --variable.
+
       --variable string-array
           Specify a set of values for Terraform-managed variables.
 

cli/testdata/coder_templates_push_--help.golden

@@ -32,6 +32,9 @@ Push a new template version from the current directory or as specified by flag
       --provisioner-tag string-array
           Specify a set of tags to target provisioner daemons.
 
+      --var string-array
+          Alias of --variable.
+
       --variable string-array
           Specify a set of values for Terraform-managed variables.