Update these batch scripts so that it's not necessary to manually spe…

…cify the paths of SAGE_LOCAL or CYGWIN_ROOT

src/bin/sage-rebase.bat

@@ -1,19 +1,32 @@
 @echo off
 rem Author:
 rem * Jean-Pierre Flori <jean-pierre.flori@ssi.gouv.fr>
+rem * Erik M. Bray <erik.bray@lri.fr>
 rem
 rem Rebase all dlls in the SAGE_LOCAL directory (and its subdirectories),
 rem but do not touch the ones already stored in the system database,
 rem and do not update it.
 rem Note that subsequent calls to 'rebaseall' will not update the Sage dlls.
 rem
-rem Invoke this script from a Windows command prompt,
-rem after adjusting SAGE_LOCAL to the Windows location of the Sage directory,
+rem Invoke this script from a Windows command prompt
 rem and, if Cygwin is installed in a non-standard location,
 rem adjusting CYGWIN_ROOT.
 
-set CYGWIN_ROOT=C:\cygwin\
-set SAGE_LOCAL=C:\cygwin\usr\local\sage\
+setlocal ENABLEEXTENSIONS
+
+set THIS_BIN=%~dp0
+
+rem SAGE_LOCAL should be one level up from the bin/ this script is in
+rem This is about the most elegant way to do this I can find thanks
+rem http://stackoverflow.com/a/33404867/982257
+call :NORMALIZEPATH "%THIS_BIN%.."
+set SAGE_LOCAL=%RETVAL%
+
+rem Cygwin saves its installation root here
+rem If there is more than one Cygwin installation on the system this
+rem will just pick up the first one
+call :READREGISTRY HKEY_LOCAL_MACHINE\SOFTWARE\Cygwin\setup rootdir
+set CYGWIN_ROOT=%RETVAL%
 
 rem Make sure bash can be called from MSDOS prompt:
 path %CYGWIN_ROOT%\bin;%path%
@@ -22,3 +35,18 @@ set CYGWIN=%CYGWIN% nodosfilewarning
 rem Call the bash script to do the real work:
 cd %SAGE_LOCAL%
 bash bin\sage-rebase.sh
+
+
+:: ========== FUNCTIONS ==========
+exit /B
+
+:READREGISTRY
+  for /F "usebackq skip=2 tokens=3" %%V in (`reg query %1 /v %2 2^>nul`) do (
+    set RETVAL=%%V
+    break
+  )
+  exit /B
+
+:NORMALIZEPATH
+  set RETVAL=%~dpfn1
+  exit /B

src/bin/sage-rebaseall.bat

@@ -2,23 +2,35 @@
 rem Authors:
 rem * Dmitrii Pasechnik <dimpase@gmail.com>
 rem * Jean-Pierre Flori <jean-pierre.flori@ssi.gouv.fr>
+rem * Erik M. Bray <erik.bray@lri.fr>
 rem
 rem Rebase all dlls in the SAGE_LOCAL directory (and its subdirectories),
 rem as well as the ones already stored in the system database,
 rem and update the database.
 rem This system-wide database is located in '/etc/rebase.db.i386' and
 rem includes the Cygwin system dlls.
 rem
-rem Invoke this script from a Windows command prompt,
-rem after adjusting SAGE_LOCAL to the Windows location of the Sage directory,
+rem Invoke this script from a Windows command prompt
 rem and, if Cygwin is installed in a non-standard location,
 rem adjusting CYGWIN_ROOT.
+rem
 rem Ensure that no other Cygwin processes are currently running.
 rem Note that you need write access to the system-wide rebase database
 rem (which usually means admin rights).
 
-set CYGWIN_ROOT=C:\cygwin\
-set SAGE_LOCAL=C:\cygwin\usr\local\sage\
+set THIS_BIN=%~dp0
+
+rem SAGE_LOCAL should be one level up from the bin/ this script is in
+rem This is about the most elegant way to do this I can find thanks
+rem http://stackoverflow.com/a/33404867/982257
+call :NORMALIZEPATH "%THIS_BIN%.."
+set SAGE_LOCAL=%RETVAL%
+
+rem Cygwin saves its installation root here
+rem If there is more than one Cygwin installation on the system this
+rem will just pick up the first one
+call :READREGISTRY HKEY_LOCAL_MACHINE\SOFTWARE\Cygwin\setup rootdir
+set CYGWIN_ROOT=%RETVAL%
 
 rem Make sure dash can be called from MSDOS prompt:
 path %CYGWIN_ROOT%\bin;%path%
@@ -27,3 +39,18 @@ set CYGWIN=%CYGWIN% nodosfilewarning
 rem Call the dash script to do the real work:
 cd %SAGE_LOCAL%
 dash bin\sage-rebaseall.sh
+
+
+:: ========== FUNCTIONS ==========
+exit /B
+
+:READREGISTRY
+  for /F "usebackq skip=2 tokens=3" %%V in (`reg query %1 /v %2 2^>nul`) do (
+    set RETVAL=%%V
+    break
+  )
+  exit /B
+
+:NORMALIZEPATH
+  set RETVAL=%~dpfn1
+  exit /B