ENH: Adding pd.__git_version__ to point to git sha commit (#21295)
- [ ] closes #21295 
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=h1) Report
> Merging [#21680](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/7a2fbce899aad302891ff9a95aeb1bd55efe533a?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21680/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #21680   +/-   ##
=======================================
  Coverage   92.05%   92.05%           
=======================================
  Files         170      170           
  Lines       50708    50708           
=======================================
  Hits        46677    46677           
  Misses       4031     4031
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.45% <ø> (ø)` | :arrow_up: |
| #single | `42.36% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=footer). Last update [7a2fbce...9421725](https://codecov.io/gh/pandas-dev/pandas/pull/21680?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 we have a once a day CI - https://github.com/pandas-dev/pandas-ci
that does a full install via pip and conda and then runs tests like a user
i believe this will fail here (these are post merge tests)

as __git_version__ would be None

can u verify? Hello @atulagrwl! Thanks for updating the PR.





Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on July 27, 2018 at 01:32 Hours UTC > we have a once a day CI - https://github.com/pandas-dev/pandas-ci
that does a full install via pip and conda and then runs tests like a user
i believe this will fail here (these are post merge tests)

I am not sure how to do that. This is my first commit to pandas and would appreciate if you tell me help me.  Merged latest master to resolve conflict in whatsnew file. @atulagrwl one more rebase, almost over the finish line. @jbrockmendel - Did the rebase and minor refactoring as suggested in test. @jreback looks about right. @atulagrwl this is almost there, mind merging in the latest changes to these files? And updating the issue ref as per @jreback comment. Im happy to take this over the line, since we haven't heard back from @atulagrwl . Will reopen a new PR and we can close this. 

CC. @jangorecki Closing in favor of #22745