Added utility to uniquely identify ghc repo states

This commit adds fingerprint.py python script that can be used to
create and restore "fingerprints" of a ghc repo configuration. A
fingerprint is a list of (sub-repo, commit) pairs. It can be used in
place of git submodules to record and reinstate the entire commit
state of the git repos used by ghc.

diff --git a/utils/fingerprint/fingerprint.py b/utils/fingerprint/fingerprint.py
new file mode 100755 (executable)
index 0000000..f04b98e
--- /dev/null
+++ b/utils/fingerprint/fingerprint.py
@@ -0,0 +1,248 @@
+#! /usr/bin/env python
+# Script to create and restore a git fingerprint of the ghc repositories.
+
+from   datetime   import datetime
+from   optparse   import OptionParser
+import os
+import os.path
+import re
+import subprocess
+from   subprocess import PIPE, Popen
+import sys
+
+def main():
+  opts, args = parseopts(sys.argv[1:])
+  opts.action(opts)
+
+def create_action(opts):
+  """Action called for the create commmand"""
+  if opts.fpfile:
+    fp = FingerPrint.read(opts.source)
+  else:
+    fp = fingerprint(opts.source)
+  if len(fp) == 0:
+    error("Got empty fingerprint from source: "+str(opts.source))
+  if opts.output_file:
+    print "Writing fingerprint to: ", opts.output_file
+  fp.write(opts.output)
+
+def restore_action(opts):
+  """Action called for the restore commmand"""
+  def branch_name(filename):
+    return "fingerprint_" + os.path.basename(filename).replace(".", "_")
+  if opts.fpfile:
+    try:
+      fp = FingerPrint.read(opts.source)
+      bn = branch_name(opts.fpfile)
+    except MalformedFingerPrintError:
+      error("Error parsing fingerprint file: "+opts.fpfile)
+    if len(fp) == 0:
+      error("No fingerprint found in fingerprint file: "+opts.fpfile)
+  elif opts.logfile:
+    fp = fingerprint(opts.source)
+    bn = branch_name(opts.logfile)
+    if len(fp) == 0:
+      error("No fingerprint found in build log file: "+opts.logfile)
+  else:
+    error("Must restore from fingerprint or log file")
+  restore(fp, branch_name=bn if opts.branch else None)
+
+def fingerprint(source=None):
+  """Create a new fingerprint of current repositories.
+
+  The source argument is parsed to look for the expected output
+  from a `sync-all` command. If the source is `None` then the
+  `sync-all` command will be run to get the current fingerprint.
+  """
+  if source is None:
+    sync_all = ["./sync-all", "log", "HEAD^..", "--pretty=oneline"]
+    source  = Popen(sync_all, stdout=PIPE).stdout
+
+  lib = ""
+  commits = {}
+  for line in source.readlines():
+    if line.startswith("=="):
+      lib = line.split()[1].rstrip(":")
+      lib = "." if lib == "running" else lib # hack for top ghc repo
+    elif re.match("[abcdef0-9]{40}", line):
+      commit = line[:40]
+      commits[lib] = commit
+  return FingerPrint(commits)
+
+def restore(fp, branch_name=None):
+  """Restore the ghc repos to the commits in the fingerprint
+
+  This function performs a checkout of each commit specifed in
+  the fingerprint. If `branch_name` is not None then a new branch
+  will be created for the top ghc repository. We also add an entry
+  to the git config that sets the remote for the new branch as `origin`
+  so that the `sync-all` command can be used from the branch.
+  """
+  checkout = ["git", "checkout"]
+
+  # run checkout in all subdirs
+  for (subdir, commit) in fp:
+    if subdir != ".":
+      cmd = checkout + [commit]
+      print "==", subdir, " ".join(cmd)
+      if os.path.exists(subdir):
+        rc = subprocess.call(cmd, cwd=subdir)
+        if rc != 0:
+          error("Too many errors, aborting")
+      else:
+        sys.stderr.write("WARNING: "+
+          subdir+" is in fingerprint but missing in working directory\n")
+
+  # special handling for top ghc repo
+  # if we are creating a new branch then also add an entry to the
+  # git config so the sync-all command is happy
+  branch_args = ["-b", branch_name] if branch_name else []
+  rc = subprocess.call(checkout + branch_args + [fp["."]])
+  if (rc == 0) and branch_name:
+    branch_config = "branch."+branch_name+".remote"
+    subprocess.call(["git", "config", "--add", branch_config, "origin"])
+
+actions = {"create" : create_action, "restore" : restore_action}
+def parseopts(argv):
+  """Parse and check the validity of the command line arguments"""
+  usage = "fingerprint ("+"|".join(sorted(actions.keys()))+") [options]"
+  parser = OptionParser(usage=usage)
+
+  parser.add_option("-d", "--dir", dest="dir",
+    help="write output to directory DIR", metavar="DIR")
+
+  parser.add_option("-o", "--output", dest="output",
+    help="write output to file FILE", metavar="FILE")
+
+  parser.add_option("-l", "--from-log", dest="logfile",
+    help="reconstruct fingerprint from build log", metavar="FILE")
+
+  parser.add_option("-f", "--from-fp", dest="fpfile",
+    help="reconstruct fingerprint from fingerprint file", metavar="FILE")
+
+  parser.add_option("-n", "--no-branch",
+    action="store_false", dest="branch", default=True,
+    help="do not create a new branch when restoring fingerprint")
+
+  parser.add_option("-g", "--ghc-dir", dest="ghcdir",
+    help="perform actions in GHC dir", metavar="DIR")
+
+  opts,args = parser.parse_args(argv)
+  return (validate(opts, args, parser), args)
+
+def validate(opts, args, parser):
+  """ Validate and prepare the command line options.
+
+  It performs the following actions:
+    * Check that we have a valid action to perform
+    * Check that we have a valid output destination
+    * Opens the output file if needed
+    * Opens the input  file if needed
+  """
+  # Determine the action
+  try:
+    opts.action = actions[args[0]]
+  except (IndexError, KeyError):
+    error("Must specify a valid action", parser)
+
+  # Inputs
+  if opts.logfile and opts.fpfile:
+    error("Must specify only one of -l and -f")
+
+  opts.source = None
+  if opts.logfile:
+    opts.source = file(opts.logfile, "r")
+  elif opts.fpfile:
+    opts.source = file(opts.fpfile, "r")
+
+  # Outputs
+  if opts.dir:
+    fname = opts.output
+    if fname is None:
+      fname = datetime.today().strftime("%Y-%m%-%d_%H-%M-%S") + ".fp"
+    path = os.path.join(opts.dir, fname)
+    opts.output_file = path
+    opts.output = file(path, "w")
+  elif opts.output:
+    opts.output_file = opts.output
+    opts.output = file(opts.output_file, "w")
+  else:
+    opts.output_file = None
+    opts.output = sys.stdout
+
+  # GHC Directory
+  # As a last step change the directory to the GHC directory specified
+  if opts.ghcdir:
+    os.chdir(opts.ghcdir)
+
+  return opts
+
+def error(msg="fatal error", parser=None, exit=1):
+  """Function that prints error message and exits"""
+  print "ERROR:", msg
+  if parser:
+    parser.print_help()
+  sys.exit(exit)
+
+class MalformedFingerPrintError(Exception):
+  """Exception raised when parsing a bad fingerprint file"""
+  pass
+
+class FingerPrint:
+  """Class representing a fingerprint of all ghc git repos.
+
+  A finger print is represented by a dictionary that maps a
+  directory to a commit. The directory "." is used for the top
+  level ghc repository.
+  """
+  def __init__(self, subcommits = {}):
+    self.commits = subcommits
+
+  def __eq__(self, other):
+    if other.__class__ != self.__class__:
+      raise TypeError
+    return self.commits == other.commits
+
+  def __neq__(self, other):
+    not(self == other)
+
+  def __hash__(self):
+    return hash(str(self))
+
+  def __len__(self):
+    return len(self.commits)
+
+  def __repr__(self):
+    return "FingerPrint(" + repr(self.commits) + ")"
+
+  def __str__(self):
+    s = ""
+    for lib in sorted(self.commits.keys()):
+      commit = self.commits[lib]
+      s += "{0}|{1}\n".format(lib, commit)
+    return s
+
+  def __getitem__(self, item):
+    return self.commits[item]
+
+  def __iter__(self):
+    return self.commits.iteritems()
+
+  def write(self, outh):
+      outh.write(str(self))
+      outh.flush()
+
+  @staticmethod
+  def read(inh):
+    """Read a fingerprint from a fingerprint file"""
+    commits = {}
+    for line in inh.readlines():
+      splits = line.strip().split("|", 1)
+      if len(splits) != 2:
+        raise MalformedFingerPrintError(line)
+      lib, commit = splits
+      commits[lib] = commit
+    return FingerPrint(commits)
+
+if __name__ == "__main__":
+  main()