-# --git generate git commit indications, as shown below
-# (this is the default if no strings are requested with -t)
-#
-# --git=object
-# generate git commit indication based on commit object only
-# (ie avoid counting commits)
-#
-# -i do not generate `+' if git-untracked files are present
-#
-# [-t[FORM]] TEXT
-# generate a form FORM containing TEXT
-# TEXT can contain newlines (final newline usually undesirable)
-# if FORM not specified, generates Arg0 Arg1 Arg2 in sequence
-# character set is SPC 0-9 a-f + * (`*' glyph is `=/=').
-#
-# We generate a physical indication of which commit was used.
-#
-# We provide for scaling factors with dynamic variables:
-# $Commitid_pixelsz if not set, we use 0.8 } multiplied
-# $Commitid_scale if not set, we use 1.0 } together
-# $Commitid_depth if not set, we use xy pixel size from above / 2
-# $Commitid_depth_scale if not set, we use 1.0 (multiplies depth above)
-#
-# For each form we have
-#
-# module Commitid_Form_2D() { ... }
-# module Commitid_Form() { ... }
-# function Commitid_Form_sz() => [ x, y ]
-#
-# These have their origin in the bottom left corner. The 3D model
-# is a positive, has its origin halfway through, and is twice the
-# depth in height, so it can be added or subtracted.
-#
-# And we provide
-#
-# function Commitid_pixelsz() // $Commitid_pixelsz * $Commitid_scale
-# function Commitid_depth() // see above
-#
-# We can generate these forms:
-#
-# Small3:
-# Small4:
-# Small5:
-# Small6:
-# Small7:
-# Small8:
-# Small9:
-# Small10:
-# git rev-list --first-parent --count HEAD
-# typically 3-4 characters but we allow for up to 6
-# padded with zeroes; if too long we reduce mod 10^n
-# eg
-# Small4 1070
-# If tree is dirty, + or * is suffixed, reducing number of
-# digits by 1.
-#
-# Small4S:
-# Small6S:
-# Small8S:
-# Small10S:
-# same but split into two lines eg
-# Small4S 10
-# 70
-#
-# Git4 Git4S
-# Git6 Git6S
-# Git8 Git8S
-# Git10 Git10S
-# git-rev-parse HEAD (prefix of requested length)
-# eg
-# Git6 82f2a2
-# If tree is dirty, + or * is suffixed to commitid,
-# reducing number of hex digits by 1.
-
-# Full3
-# Full4
-# Full5
-# Full6
-# Full7
-# Full8
-# Full9
-# Full10
-# git-rev-list --first-parent --count HEAD
-# git-rev-parse HEAD
-# eg
-# Full6 1070
-# 82f2a2
-# If tree is dirty, + or * is suffixed to count (but not to
-# commitid) reducing number of digits by 1.
+# --git Generate git commit indications, as shown below
+# (this is the default if no strings are requested with -t).
+# Ie, produce the `Autoscaling modules' and `Specific layouts'.
+#
+# --git=objid
+# Generate git commit indication based on commit object only
+# (ie avoid counting commits). Ie, do not generate `Small'
+# and `Full' layouts (and never select them for `Best').
+#
+# -i Do not generate `+' dirty indication if git-untracked files
+# are present (ie, missing .gitignore entries). The `*'
+# dirty tree indication (for modified files) cannot be disabled.
+#
+# [-t[LAYOUT]] TEXT
+# Generate a layout LAYOUT containing TEXT. TEXT can
+# contain newlines (a final newline usually undesirable, as
+# it will generate a blank line). If LAYOUT is not specified,
+# generates Arg0, Arg1, Arg2, etc., for successive such
+# TEXTs. The permissible character set in is TEXT is:
+# space 0-9 a-f + *
+#
+#
+# OPENSCAD INTERFACE
+# ==================
+#
+# Dynamic variables for configuration
+# -----------------------------------
+#
+# We honour the following variables to control various scaling factors:
+#
+# default value notes
+# $Commitid_pixelsz 0.8 \ multiplied together
+# $Commitid_scale 1.0 /
+# $Commitid_depth pixelsz/2 \ multiplied together
+# $Commitid_depth_scale 1.0 /
+# $Commitid_max_best_scale 2.0 limits XY scaling in *Best*
+#
+# FYI the font is nominally 3x5 pixels, with 1-pixel inter-line and
+# inter-character gaps. (It's not strictly speaking a 3x5 bitmap
+# font, size it contains partial pixels and diagonals.)
+#
+#
+# Non-`module'-specific functions
+# -------------------------------
+#
+# We provide the following functions (which depend on the config
+# variables, but not on anything else) and compute useful values:
+#
+# function Commitid_pixelsz() Actual size of each nominal pixel
+# function Commitid_depth() Depth to use (the amount characters
+# should be raised or sunken)
+#
+# General form of provided openscad modules
+# -----------------------------------------
+#
+# module Commitid_MODULE_2D(...) Collection of polygons forming characters
+# module Commitid_MODULE(...) The above, extruded up and down in Z
+# module Commitid_MODULE_M_2D(...) Mirror writing
+# module Commitid_MODULE_M(...) 3D mirror writing
+# function Commitid_MODULE_sz() A 2-vector giving the X,Y size
+#
+# Except for *Best* modules, the XY origin is in the bottom left
+# corner without any margin. Likewise Commitid_MODULE_sz does not
+# include any margin.
+#
+# For 3D versions, the model is 2*depth deep and the XY plane bisects
+# the model. This means it's convenient to either add or subtract from
+# a workpiece whose face is in the XY plane.
+#
+# The _M versions are provided to avoid doing inconvenient translation
+# and rotation to get the flipped version in the right place.
+#
+#
+# Autoscaling modules
+# -------------------
+#
+# These modules take a specification of the available XY space, and
+# select and generate a suitable specific identification layout:
+#
+# module Commitid_BestCount_2D (max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestCount (max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestCount_M_2D(max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestCount_M (max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestObjid_2D (max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestObjid (max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestObjid_M_2D(max_sz, margin=Commitid_pixelsz())
+# module Commitid_BestObjid_M (max_sz, margin=Commitid_pixelsz())
+#
+# max_sz should be [x,y].
+#
+# BestCount includes (as much as it can of) the git commit count,
+# ie the result of
+# git rev-list --first-parent --count HEAD
+# (and it may include some of the git revision ID too).
+#
+# BestObjid includes as much as it can of the git commit object hash,
+# and never includes any of the count.
+#
+# All of these will autoscale and autorotate the selected model, and
+# will include an internal margin of the specified size (by default,
+# one pixel around each edge). If no margin is needed, pass margin=0.
+#
+# There are no `function Commitid_Best*_sz'. If they existed they
+# would simply return max_sz.
+#
+#
+# Output format
+# -------------
+#
+# In general the output, although it may be over multiple lines,
+# is always in this order
+# git commit object id (hash)
+# dirty indicator
+# git commit count
+#
+# Not all layouts have all these parts. The commit object id may
+# sometimes be split over multiple lines, but the count will not be.
+# If both commit id and commit count appear they will be separated
+# by (at least) a newline, or a dirty indicator, or a space.
+#
+# The commit id is truncated to fit, from the right.
+#
+# The commit count is truncated from the _left_, leaving the least
+# significant decimal digits.
+#
+# The dirty indicator can be
+#
+# * meaning the working tree contains differences from HEAD
+#
+# + meaning the working tree contains untracked files
+# (ie files you have failed to `git add' and also failed
+# to add to gitignore). (But see the -i option.)
+#
+#
+# Specific layouts
+# ----------------
+#
+# If you want to control the exact layout (and make space for it in
+# your design), you can use these:
+#
+# module Commitid_LAYOUT_2D()
+# module Commitid_LAYOUT()
+# module Commitid_LAYOUT_M_2D()
+# module Commitid_LAYOUT_M()
+# function Commitid_LAYOUT_sz()
+#
+# Here LAYOUT is one of the following (giving for example, `module
+# Commitid_Full8_2D'). In the examples, we will assume that the tree
+# is dirty, the commit count is 123456, and the commit object id
+# starts abcdeffedbcaabcdef... In the examples `_' shows where a
+# space would be printed.
+#
+# Small2 Small3 ... Small10
+# A single line containing as much of the count will fit, eg:
+# Small5 3456*
+# Small8 _*123456
+# The objectid is included if more than one character of of it
+# will fit without makign the output ambiguous:
+# Small9 ab*123456
+#
+# Small2S Small4S ... Small10S
+# Small3T Small9T
+# Same as Small but split into two lines (S)
+# or three lines (T). Eg:
+# Small4S *4 Small6T _*
+# 56 34
+# 56
+# Git2 Git3 ... Git10
+# Git4S Git6S ... Git10S
+# Git6T Git9T
+# Just the commit object hash, in one, two (S) or three (T)
+# lines. E.g.:
+# Git5 abcd*
+#
+# Full4 Full6 ... Full20:
+# The commit object hash plus the commit count, on
+# separate lines, eg:
+# Full6 abcdef Full8 abcdeffe
+# *23456 _*123456
+#
+# Full6T Full9T ... Full30T
+# As Full but the commit object id is split over two lines
+# producing a 3-line layout, eg:
+# Full9T abc Full21T abcdeff
+# de* edbcaa*
+# 456 _123456
+#
+# Other LAYOUTs
+# -------------