Update merging.rst
After having a small issue at #17552 I realized that this text could be more explicit.

- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=h1) Report
> Merging [#17556](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/f5cfdbb1f4b715819aceac4b00cf18ba5f467f85?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17556/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17556      +/-   ##
==========================================
- Coverage   91.25%   91.23%   -0.02%     
==========================================
  Files         163      163              
  Lines       49614    49614              
==========================================
- Hits        45274    45265       -9     
- Misses       4340     4349       +9
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.02% <ø> (ø)` | :arrow_up: |
| #single | `40.19% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17556?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/17556?src=pr&el=footer). Last update [f5cfdbb...80a1104](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=h1) Report
> Merging [#17556](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/40e19bb8451a44923ddf10e3e534a6243f967ff9?src=pr&el=desc) will **decrease** coverage by `0.07%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/17556/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #17556      +/-   ##
==========================================
- Coverage   91.25%   91.17%   -0.08%     
==========================================
  Files         163      163              
  Lines       49617    49664      +47     
==========================================
+ Hits        45277    45281       +4     
- Misses       4340     4383      +43
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.02% <ø> (ø)` | :arrow_up: |
| #single | `40.19% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9jb25jYXQucHk=) | `97.6% <ø> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/api.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXBpLnB5) | `87.5% <0%> (-12.5%)` | :arrow_down: |
| [pandas/core/indexes/interval.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9pbnRlcnZhbC5weQ==) | `90.5% <0%> (-3.08%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `94.73% <0%> (-0.8%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.77% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/17556?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/17556?src=pr&el=footer). Last update [40e19bb...9c12863](https://codecov.io/gh/pandas-dev/pandas/pull/17556?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @1kastner : Thanks for this PR!  Before we merge this, you'll need to update the doc-string for `pandas.concat` in the codebase.  You can find the function in `pandas/core/reshape.py` Hello @1kastner! Thanks for updating the PR.



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

##### Comment last updated on September 17, 2017 at 20:18 Hours UTC Closed because of insufficient elaboration of feedback and different ideas of how explicit (and therefore long) the documentation should be. I would have prefered the documentation to be longer. @1kastner : No need to be this hasty to close it.  We have time to work this out.