Description of problem:
Invoking capsule sync:
1) Sat orders capsule to sync _all_ repositories in _all_ content views / lifecycle environments to the capsule
2) for every such repository, pulp on the capsule generates new repo metadata

Assume a use case where Sat having few hundreds of repositories in different content views, and just some repo might need to be synced (as there are doubts if it was synced properly). A capsule sync would do so so much redundant work taking hours.

To see the scope of ridiculous work being done:
- assume a use case where large repos (say rhel5-7 base) are present in many content views as a base - repo metadata takes nontrivial time to be computed, multiply it by # of repos..
- particular example: a customer behind this bug has 1250 repos and capsule sync takes 3-4 hours(!) doing nothing

Please optimize either 1 or 2. While I understand Sat does not know what repo needs and what does not need to be synced to the capsule (i.e. 1 sounds legit), there should be an option to e.g. fetch metadata from Sat to Caps, compare if they are the same and if so, do nothing (and if differ or missing on Caps, then do the sync).


Version-Release number of selected component (if applicable):
Sat 6.1.7


How reproducible:
100%


Steps to Reproduce:
1. Have more pulp repos enabled (e.g. have sat61-tools repo in 10 published content views)
2. do repeatedly capsule sync, without any repo / content view manipulation meantime
3. Check times of execution of 1st sync and other synces
4. ll /var/lib/pulp/published/yum/https/repos/Default_Organization/Library/ContentViewName1/content/dist/rhel/server/7/7Server/x86_64/sat-tools/6.1/os/repodata/


Actual results:
3. synces takes the same/very similar time, nontrivial
4. repodata recalculated every time


Expected results:
3. sync takes small time, if no work to be done
4. repodata not updated / recalculated every time (if there is no need to)


Additional info: