The problem is that sysadmins don't know everything.
> in the year 2015, pip went from version 1.5.6 to 8.1.1
The only releases in 2015 were 6.x and 7.x.
There were 8 documented backwards incompatibilities, 4 deprecated the previous year, and 3 documenting a couple bugs that were fixed several days after the 7.0.0 release.
These are the sorts of thing an aware Python developer will know.
You're right; it was the period from December 22nd, 2014 to March 17th, 2016, so about 15 months centered around 2015.
We may be counting regressions differently; I'm including both adding and removing the spinner as a regression, for instance (since both the addition and removal added unexpected behavior).
Note that the undeniable regressions that occurred in releases during those 15 months included:
1. Exceptions raised in any command on Windows
2. Switching from not installing standard libraries to installing them back to not installing them
3. Blocking if the particular server pypi.python.org was down
4. An infinite loop on filesystems that do not allow hard links
Note that in that time they also added yet another internal package management system (incompatible with the existing two), changed the versioning semantics twice, and dropped support for versions of python that were 3 years old at that point.
And, again, there's nothing particularly wrong with or bad about pip; this is just what a younger generation of developers are used to.
> in the year 2015, pip went from version 1.5.6 to 8.1.1
The only releases in 2015 were 6.x and 7.x.
There were 8 documented backwards incompatibilities, 4 deprecated the previous year, and 3 documenting a couple bugs that were fixed several days after the 7.0.0 release.
These are the sorts of thing an aware Python developer will know.