*TLDR: Or at least a rough estimate of how long you've spent on a project.
It's very easy, even for the most disciplined of teams, to become so involved in a project that agile stories and time trackers go out the window; the only goal is to finish. We had this happen on a project last year and it made it very hard to see where the time went during our project retrospective. We knew we'd been working constantly, but on what? Knowing that we did diligently commit our code to Git made me wonder if there was a way to approximate time spent based on commit timestamps.
Turns out, several people had already been working on this and we settled on a ruby gem from Frank Rietta. You can read more about the assumptions used in calculations over at his site and GitHub, but it couldn't be easier to install:
Installing is easy from your computer with Ruby installed. From the command line, run: gem install git_time_extractor Then go one of your GIT project directories, and run: git_time_extractor > output_time.csv
The reason I picked this tool over others is that the spreadsheet generated can be manipulated in whatever way need for records, sort by employee, what took the longest, how much time did we spend in total etc.