When using `static_transform_publisher`, attempting to link to coordinate systems via a common frame the publisher removes the link from one tree and places it in the other. This happens both with `tf` and `tf2_ros`, and when execucted from the command line as well as from a launch file.
See the following example where `ar_marker_master` and `ar_marker_0` refer to the same point in world space. Without linking the two using `tf`, the `tf_tree` looks like this:
Then, we can attempt to link the two frames using:
```
rosrun tf static_transform_publisher 0 0 0 0 0 0 /ar_marker_master /ar_marker_0 1000
```
Where the resulting tree looks like this:
This successfully links `ar_marker_master` with `ar_marker_0`, but notice that the link `ar_marker_0` has been removed from the tree with `camera_link`. Shouldn't this join the two trees?
For more context, if I run `rosrun tf tf_echo /camera_color_optical_frame /ar_marker_0` to view the transformation between `camera_color_optical_frame` and `ar_marker_0` before the adding the link, I can see:
```
At time 1556317303.088
- Translation: [-0.380, 0.338, 1.264]
- Rotation: in Quaternion [0.966, 0.072, -0.068, 0.237]
in RPY (radian) [2.669, 0.166, 0.109]
in RPY (degree) [152.939, 9.504, 6.273]
```
But after running `static_transform_publisher`:
```
Exception thrown:Could not find a connection between 'camera_color_optical_frame' and 'ar_marker_0'
```
Where did the link go? And, if this is not the proper way to join two trees, how should I perform the transform to join the two coordinate systems?
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