I recently had the pleasure of reading through a selection of commits from the sympy repository. The output I saw:

ca9fcd7839 eae25630 2017-11-16@13:37:22 Update mod.py
7a1852f73b eae25630 2018-03-13@23:56:35 Fixed issue #14489
7bfe01fa87 eae25630 2018-03-14@00:51:11 Remove useless import
f11327fa6e eae25630 2018-06-15@16:33:24 Merging changes
7f8b0a00ae eae25630 2018-06-15@17:09:17 Revert "Merging changes"
ae4b6d621d eae25630 2018-12-06@05:18:04 modified mod
b3c0f96255 04d3b1ab 2018-12-06@17:33:22 added test into test_arit
bbe3449c3d 04d3b1ab 2018-12-18@23:19:54 Fixing tests
6bc995680c eae25630 2019-01-05@17:56:00 Made changes to fix the issue #15493

(This output was generated by this script , searching for the blobs seen in column 2)

I am publishing this output to provide an example of how not to write a commit message. Those summaries are (almost) completely meaningless. I can see that ‘mod’ is being changed, and I can tell that some commits are (probably) only changing some tests, but for the most part these commit summaries are utterly and completely useless. When you write a commit message, you must convey information. What does the commit do? Include meta-data like the issue being changed in the trailers, not in the summary, and never write a commit message like “Merging changes”!! The whole point of the commit summary is to allow a reader to have a high level view of how the commit changes the repository. For all of those commits, that information is missing. To gather than information, the commit must be inspected.