diff --git a/common/save_commit_refs.py b/common/save_commit_refs.py
new file mode 100755
index 0000000..3987db1
--- /dev/null
+++ b/common/save_commit_refs.py
@@ -0,0 +1,182 @@
+#!/usr/bin/env python3
+#--------------------------------------------------------------------
+#
+# save_commit_refs.py
+#
+# This file is used to annotate a standard tech information JSON
+# file.  Each JSON file should have a section called "reference"
+# (if not, this script exits without doing anything).  The
+# "reference" section contains the commit hashes of repositories
+# used by the developer for generating the PDK, creating a
+# reference against which issues can be compared.  The "reference"
+# section is fixed and is not modified by replacement like the
+# rest of the JSON file.  It is the duty of the PDK developer to
+# update the references section periodically by running "make
+# distribution".
+#
+#--------------------------------------------------------------------
+# Usage:
+#
+#	save_commit_refs.py <filename> [-D<variable> ...]
+#
+# Where <filename> is the name of a technology JSON file, and
+# <variable> may be a <keyword>=<hash_value> pair only.
+# <keyword> corresponds to the variable name in a technology Makefile
+# for a commit hash that appears somewhere in <filename>.  <value>
+# is the commit hash value corresponding to <keyword>.
+#
+# The JSON file "reference" section is expected to have entries of
+# the form
+#	"<name>": "<commit_hash>"
+#
+# where <name> must also appear elsewhere in <filename> in an entry
+# of the form
+#	"<name>": "<keyword>"
+#
+# Then, where "-D<keyword>=<hash_value>" has been passed to the
+# script on the command line, the entry in the "reference" section
+# is changed by replacing "<commit_hash>" with "<hash_value>".
+#
+# The output of the script overwrites <filename> with the modified
+# contents.
+#
+# Example:
+#	sky130.json has an entry in "distribution":
+#		"magic": "fe2eb6d3906ed15ade0e7a51daea80dd4e3846e2"
+#	reflecting the git commit number of the program "magic" at
+#	the time the developer last ran save_commit_refs.py.
+#	Elsewhere in sky130.json, the following line appears:
+#		"magic": "MAGIC_COMMIT"
+#	If save_commit_refs.py is called as:
+#		save_commit_refs.py sky130.json -DMAGIC_COMMIT=abcdef
+#	then the line in "distribution" will be changed to:
+#		"magic": "abcdef"
+#
+#--------------------------------------------------------------------
+
+import os
+import re
+import sys
+
+def runsubs(keys, defines, inputfile, outputfile):
+
+    ifile = False
+    ifile = open(inputfile, 'r')
+    if not ifile:
+        print("Error:  Cannot open file " + inputfile + " for reading.\n", file=sys.stderr)
+        return
+
+    indist = False
+
+    filetext = ifile.readlines()
+    lastline = []
+
+    # Input file has been read, so close it.
+    ifile.close()
+
+    # Open output file
+    if not outputfile:
+        outputfile = inputfile
+
+    ofile = open(outputfile, 'w')
+    if not ofile:
+        print("Error:  Cannot open file " + outputfile + " for writing.\n", file=sys.stderr)
+        return
+
+    keyrex = re.compile('[ \t]*"([^"]+)":[ \t]*"[^"]+"')
+    valuerex = re.compile('[ \t]*"[^"]+":[ \t]*"([a-z0-9]+)"')
+    distdefs = {}
+    defs = []
+
+    for line in filetext:
+        newline = line
+
+        if indist == False:
+            if '"distribution":' in line:
+                indist = True
+            else:
+                # Find values matching keywords
+                for key in keys:
+                    if key in line:
+                        kmatch = keyrex.match(line)
+                        if kmatch:
+                            print('Found match "' + kmatch.group(1) + '" for key "' + key + '"')
+                            distdefs[kmatch.group(1)] = defines[key]
+                            defs.append(kmatch.group(1))
+        else:
+            # Find definitions matching keywords
+            for defx in defs:
+                if defx in line:
+                    vmatch = valuerex.match(line)
+                    if vmatch:
+                        value = distdefs[defx]
+                        newline = line.replace(vmatch.group(1), value)
+
+        print(newline, file=ofile, end='')
+
+    ofile.close()
+    return
+
+def printusage(progname):
+    print('Usage: ' + progname + ' filename [-options]')
+    print('   Options are:')
+    print('      -help         Print this help text.')
+    print('      -quiet        Stop without error if input file is not found.')
+    print('      -ccomm        Remove C comments in /* ... */ delimiters.')
+    print('      -D<def>       Define word <def> and set its value to 1.')
+    print('      -D<def>=<val> Define word <def> and set its value to <val>.')
+    print('      -I<dir>       Add <dir> to search path for input files.')
+    return
+
+if __name__ == '__main__':
+
+   # Parse command line for options and arguments
+    options = []
+    arguments = []
+    for item in sys.argv[1:]:
+        if item.find('-', 0) == 0:
+            options.append(item)
+        else:
+            arguments.append(item)
+
+    if len(arguments) > 0:
+        inputfile = arguments[0]
+        if len(arguments) > 1:
+            outputfile = arguments[1]
+        else:
+            outputfile = []
+    else:
+        printusage(sys.argv[0])
+        sys.exit(0)
+
+    defines = {}
+    keys = []
+    for item in options:
+        result = item.split('=')
+        if result[0] == '-help':
+            printusage(sys.argv[0])
+            sys.exit(0)
+        elif result[0][0:2] == '-D':
+            keyword = result[0][2:]
+            value = result[1]
+            defines[keyword] = value
+            keys.append(keyword)
+        else:
+            print('Bad option ' + item + ', options are -help, -D<def>\n')
+            sys.exit(1)
+
+    if not os.path.isfile(inputfile):
+        if not quiet:
+            print("Error:  No input file " + inputfile + " found.")
+        else:
+            sys.exit(0)
+
+    runsubs(keys, defines, inputfile, outputfile)
+
+    # Set mode of outputfile to be equal to that of inputfile (if not stdout)
+    if outputfile:
+        statinfo = os.stat(inputfile)
+        mode = statinfo.st_mode
+        os.chmod(outputfile, mode)
+
+    sys.exit(0)