TeXnicCenter produces a status file named *.tps which holds information on currently open *.tex files and window positions. This most likely should not be checked in.

The xy package generates *.xyd files whenever the commands

    \MakeOutlines
    \OnlyOutlines
    \ShowOutlines
    \NoOutlines

are present in the LaTeX source. These automatically-generated files
contain the dimensions of figures typeset with xy and are recreated as
needed. This is documented on pp. 15f. of the XY-pic Reference Manual
(1999/02/16).

As automatically-generated, temporary files, they should be ignored.

package not interfere with makeindex's style files

.ist files are makeindex style files, which determine how a
makeindex-generated index will look like. Therefore, they must be
included in source control.

The `vhistory` package generates two files, with `.hst` and `.ver` extensions.

This is the default extension the package "tcolorbox" may generate. The actual extension may be changed by key "listing file" provided by "tcolorbox".

Added LyX editor backup file extension: i,e .lyx~

This reverts commit d878f045.

Source: https://texdoc.net/pkg/xmpincl -> page 3:

> basically create a new file .xmpi

Added a temporary file used in MacTeX

* without . the auto directory is still considered for commits

* small addition that ensures all Emacs-Lisp files (.el files) are ignored

The presentation software pdfpc [1] (which is handy for latex beamer slides) supports additional notes on the secondary screen provided by *.pdfpc files.
These can be autogenerated from latex documents with the pdfpcnotes package [2], thus should be ignored in a latex project (but not in others where they could have been created manually).

[1] https://pdfpc.github.io/
[2] https://github.com/cebe/pdfpc-latex-notes

minitoc also generates .stc, .slf, and .slt files

- .soc - package changes
- .spl - documentclass elsarticle (Elsevier journals)

Source: http://tex.stackexchange.com/a/256803/9075

The `endnotes` package generates `*.ent` files. These should also be
ignored.

Add missing beamer temporary file extension

Added a line that adds the `auto` folder that Emacs+ AUCTex automatically creates in the gitignore list. 

More about this `auto` feature below 
https://www.gnu.org/software/auctex/manual/auctex/Parsing-Files.html

See documentation at
https://github.com/gregorio-project/gregorio