Issue operator-framework#407: Docs for version range support

Add docs explaining version range.

Signed-off-by: Michael Ryan Peter <mipeter@redhat.com>

docs/drafts/version-ranges.md

@@ -0,0 +1,49 @@
+# Operator version ranges
+
+This document explains how to specify a version range to install or update an Operator with OLM 1.0.
+
+You define an Operator's target version in its custom resource (CR) file.
+The following list describes how OLM resolves an Operator's target version, and the resulting actions:
+
+Not specifying a version in the CR
+: Installs or updates the latest version of the Operator.
+Updates are applied automatically when they are published to the catalog.
+
+Specifying a version in the CR
+: Installs or updates the specified version.
+Updates are not applied automatically.
+If you want to update the Operator, you must manually edit the CR and apply the changes to the cluster.
+
+Specifying a channel
+: Installs or updates the latest version of the Operator in the channel.
+Updates are applied automatically when they are published to the specified channel.
+
+Specifying a version range in the CR
+: Installs or updates the latest version of the Operator within the version range.
+Updates that are within the specified range are automatically installed.
+Updates that are outside of the specified range are not installed.
+
+The `spec.version` field uses the Masterminds `semver` package to enable the version range functionality.
+
+OLM 1.0 does not support following methods for specifying a version range:
+
+* Using tags and labels are not supported.
+You must use semantic versioning to define a version range.
+* Using [hypen range comparisons](https://github.com/Masterminds/semver#hyphen-range-comparisons) are not supported.
+For example, the following range option is not supported:
+
+  ```yaml
+  version: 3.0 - 3.6
+  ```
+
+  To specify a range option, use a method similar to the following example:
+
+  ```yaml
+  version: >=3.0 <3.6
+  ```
+
+You can use the `x`, `X`, and `*` characters as wildcard characters in all comparison operations.
+
+For more information about parsing, sorting, checking, and comparing version constraints, see the [Masterminds SemVer README](https://github.com/Masterminds/semver#semver).
+
+## Example CRs that specify a version range