We are very happy to receive suggestions which fix typos, formatting, and obvious mathematical errors; which clarify exposition in a straightforward way; or which add new technical functionality (such as versions for other devices). We are not asking for new mathematical content from the public at this time.

We are very grateful to everyone who is showing interest in our project, and to anyone who helps us improve it! However, in order to avoid any misunderstanding later, we should mention upfront that your contributions will only be recorded on github commit logs, but not in the book itself (because the book is officially an IAS project).

Note that the version of the book you are working from (including the version posted on the public web site) may not be the most recent one. If you've found an error and want to check whether it has already been corrected in the most recent version, you may need to clone the git repository and compile the sources yourself, or else look at the source code on github.

If you only want to point out the existence of an error or make a general suggestion, you can open an issue on the github project. The authors will (eventually) respond and either implement a fix or decide that no fix is necessary. If you would like to fix an error yourself or suggest a specific concrete change, you can fork the github project, commit the change in a branch on your fork, and open a pull request to the parent project.

Please make sure that your pull request is attached to the correct branch. Changes which add new mathematics, or which alter the numbering of existing sections, theorems, or equations, must wait for the second edition. Other changes, as long as they are not of unreasonable size, can be released as updates to the first edition. To ensure that your change does not alter existing numberings, you can run "make labelcheck".

Corrections of mathematical typos and other errors, as well as changes in exposition, should also be listed in the errata for the first edition (errata.tex).

• The first column in the errata table should be the nearest surrounding numbered label, be it a section, theorem, or exercise.

• The second column is obtained by running git describe on the commit where the fix was merged into the master branch. You don't know this when writing your fix, of course, so the correct thing to put here is a comment of the form

  % merge of 1234567
  

  where 1234567 is the commit hash in which you made the fix. (This necessitates making two commits, one to make the fix and one to record the erratum.) Please use exactly this syntax so that it can be automatically updated by the errata-marking script.

• The third column is a description of the change. Please be specific enough that someone looking at only a printed version (which may have page breaks in different places) could easily find its location.

It is generally a good idea not to submit github pull requests from your master branch. This is because whatever branch you submit a pull request from, any new commits on that branch that happen before the pull request is merged get added to the pull request. Thus, if you submit pull requests from your master branch, you cannot have multiple unrelated pull requests open at once, or do unrelated work on your master branch before your pull request is merged. To create a special branch for your pull request, run

git checkout -b BRANCHNAME

Make your commits in that branch, then run

git push origin BRANCHNAME:BRANCHNAME

assuming that your git remote origin is set up to be your github fork (rather than the main HoTT/book repository). The main page of your github fork should then have a little prompt asking you whether you want to issue a pull request from your most recently pushed branch.