make Git versioning resilient to non-git tarballs

closes nrnrnr#24

CHANGES

@@ -1,4 +1,5 @@
 CHANGES FOR VERSION 2.13
+binaries now track which git version they are
 support for LaTeX is updated to use \rmfamily, \bfseries, and so on
 Fixed indentation issue https://github.com/nrnrnr/noweb/issues/24 
 add \@nwbegincodelinewidth to help typeset code chunks in list items

src/INSTALL

@@ -23,6 +23,13 @@ either Icon or Awk, but Icon is better:
     (This breaking change was put in to enable the Awk and Icon codes
     to generate *identical* outputs, for regression testing.)
 
+  - As of version 2.13, the `c/Makefile` contains a GNU-ism.
+    If you don't have GNU Make, you'll need to find the use of
+    `$(wildcard ...)` and expand it manually.  If you're not using
+    `git`, remove the dependency.  If you are using git,
+    change the invocation of `wildcard` to hold just the path 
+    name to `master`.
+
 
 To build noweb:
 

src/c/Makefile

@@ -92,7 +92,7 @@ doc.ps: doc.dvi
 markup.ps: markmain.nw
 	notangle -Rmarkup.dot markmain.nw | dot -Tps > $@
 
-gitversion.c: ../gitversion ../../.git/refs/heads/master
+gitversion.c: ../gitversion $(wildcard ../../.git/refs/heads/master)
 	echo 'const char gitversion[] = "'"$$(../gitversion -prefix)"'";' > $@
 
 

src/gitversion

@@ -5,4 +5,22 @@ case $1 in
   *) prefix="" ;;
 esac
 
-echo "$prefix$(git describe --abbrev=20  --dirty --always --tags)"
+notversioned="${prefix}Not under Git versioning"
+
+search=.
+
+while [ ! -r "$search/.gitversionmark" ]; do
+  search="$search/.."
+  case $search in
+    ./../../../../../../..*) echo "$0: Cannot find git version mark"
+                             echo "$notversioned"
+                             exit 
+                             ;;
+  esac
+done
+
+if [ -r "$search/.git/refs/heads/master" ]; then
+  echo "$prefix$(git describe --abbrev=20  --dirty --always --tags)"
+else
+  echo "$notversioned"
+fi