A tool for editing version-control repository history, reposurgeon enables risky operations that version-control systems don't want to let you do, such as editing past comments and metadata and removing commits. It works with any version control system that can export and import git fast-import streams, including git, hg, bzr, CVS, and RCS. It can also read Subversion dump files directly, and can thus be used to script production of very high-quality conversions from Subversion to any supported DVCS.
doclifter helps with lifting documents with nroff markup to XML-DocBook. Lifting documents from presentation level to semantic level is hard, and a really good job requires human polishing. This tool aims to do everything that can be mechanized, and to preserve any troff-level information that might have structural implications in XML comments. TBL tables are translated into DocBook table markup, PIC into SVG, and EQN into MathML (relying on pic2svg and GNU eqn for the last two).
Dateutils are a bunch of tools that revolve around fiddling with dates and times in the command line, with a strong focus on use cases that arise when dealing with large amounts of financial data. Their target market is shell scripts that need date calculations or calendar conversions, and as such they are highly pipe-able and modeled after their well-known cousins (e.g. dtest vs. test, or dgrep vs. grep).
ascii lists ASCII idiomatic names and octal/decimal code-point forms. It provides easy conversion between various byte representations and the American Standard Code for Information Interchange (ASCII) character table. It knows about a wide variety of hex, binary, octal, Teletype mnemonic, ISO/ECMA code point, slang names, XML entity names, and other representations. Given any one on the command line, it will try to display all others. Called with no arguments, it displays a small, handy ASCII chart.
deheader analyzes C and C++ files to determine which header inclusions can be removed while still allowing them to compile. This may result in substantial improvements in compilation time, especially on large C++ projects. It also sometimes exposes dependencies and cohesions of which developers were unaware.
yuck is a command line option parser for C that works on a minimal set of dependencies - only a C compiler and the m4 macro processor are required. It supports all the standard use cases: GNU-style long options (--option), condensable short options (-xab for -x -a -b), and optional arguments to long and short options (--foo[=BAR]), multiple occurrence of options (-vvv). Most importantly, it does not depend on libc's getopt() nor getopt_long().