Reuse Content from other repos

[pulpbot]

Author: @fao89 (fao89)

Redmine Issue: 6344, https://pulp.plan.io/issues/6344

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If two repositories have some identical content, then Pulp should be able to re-use that content. This is true even if the content is placed in differing locations in the two repositories. Do the following:

Scenario 1:

1. Create a pair of repositories. Give the two repositories a download policy of either on demand or streamed. Give the two repositories differing urls, where the urls reference a pair of repositories with some identical content and differing layouts.
2. Sync each of the repositories.
3. Publish each of the repositories.
4. Fetch an identical content unit from each of the two repositories.

Scenario 2:

1. Create a pair of repositories. Give the two repositories a download policy of either on demand or streamed. Give the two repositories differing urls, where the urls reference a pair of repositories with some identical content and differing layouts.
2. Sync each of the repositories.
3. Re-sync each of the repositories.
4. Publish each of the repositories.
5. Fetch an identical content unit from each of the two repositories.

References: #6229 #6303