[PATCH] New script and module: gitlog-to-changelog

[Jim Meyering]

With the proliferation of "topic branches" in my work-flow, it is not
effective for me to version-control ChangeLog files (too many pointless
conflicts).  So, for projects that I control, I am transitioning away
from that.  However, I find ChangeLog files very useful not just for
reference, but also for the discipline imposed when a well-written entry
must accompany every commit.

Instead, now, I compose ChangeLog entries solely in git log messages and
use the following script to generate a ChangeLog file at "make dist" time.

Here's a sample rule (from a top-level Makefile.am)
to generate a ChangeLog file from post-2008-01-01 log entries
into the distribution tarball:

dist-hook:
        if test -d .git; then                                           \
          $(top_srcdir)/build-aux/gitlog-to-changelog --since=2008-01-01 \
            > $(distdir)/cl-t;                                          \
          rm -f $(distdir)/ChangeLog;                                   \
          mv $(distdir)/cl-t $(distdir)/ChangeLog;                      \
        fi

One final point: automake requires that there be a top-level
ChangeLog file, so I've added this to bootstrap.conf:

    # Automake requires that ChangeLog exist.
    touch ChangeLog

For a real live example of a package using this, see idutils:

  http://git.sv.gnu.org/gitweb/?p=idutils.git

Coreutils is next.

Here's what I've just pushed to gnulib:

        New script and module: gitlog-to-changelog
        * MODULES.html.sh (maint+release support): Add gitlog-to-changelog.
        * modules/gitlog-to-changelog: New file.
        * build-aux/gitlog-to-changelog: New file.

Signed-off-by: Jim Meyering <address@hidden>
---
 MODULES.html.sh               |    1 +
 build-aux/gitlog-to-changelog |  174 +++++++++++++++++++++++++++++++++++++++++
 modules/gitlog-to-changelog   |   19 +++++
 3 files changed, 194 insertions(+), 0 deletions(-)
 create mode 100755 build-aux/gitlog-to-changelog
 create mode 100644 modules/gitlog-to-changelog

diff --git a/MODULES.html.sh b/MODULES.html.sh
index f6c9853..4e3f2f2 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -2731,6 +2731,7 @@ func_all_modules ()
   func_module announce-gen
   func_module autobuild
   func_module git-version-gen
+  func_module gitlog-to-changelog
   func_module gnupload
   func_module maintainer-makefile
   func_module vc-list-files
diff --git a/build-aux/gitlog-to-changelog b/build-aux/gitlog-to-changelog
new file mode 100755
index 0000000..1b7a659
--- /dev/null
+++ b/build-aux/gitlog-to-changelog
@@ -0,0 +1,174 @@
+#!/usr/bin/perl
+# Convert git log output to ChangeLog format.
+
+my $VERSION = '2008-02-09 13:52'; # UTC
+# The definition above must lie within the first 8 lines in order
+# for the Emacs time-stamp write hook (at end) to update it.
+# If you change this file with Emacs, please let the write hook
+# do its job.  Otherwise, update this string manually.
+
+# Copyright (C) 2008 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Written by Jim Meyering
+
+use strict;
+use warnings;
+use Getopt::Long;
+use POSIX qw(strftime);
+
+(my $ME = $0) =~ s|.*/||;
+
+# use File::Coda; # http://meyering.net/code/Coda/
+END {
+  defined fileno STDOUT or return;
+  close STDOUT and return;
+  warn "$ME: failed to close standard output: $!\n";
+  $? ||= 1;
+}
+
+sub usage ($)
+{
+  my ($exit_code) = @_;
+  my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR);
+  if ($exit_code != 0)
+    {
+      print $STREAM "Try `$ME --help' for more information.\n";
+    }
+  else
+    {
+      print $STREAM <<EOF;
+Usage: $ME [OPTIONS]
+
+Convert git log output to ChangeLog format.
+
+OPTIONS:
+
+   --since=DATE convert only the logs since DATE;
+                  the default is to convert all log entries.
+
+   --help       display this help and exit
+   --version    output version information and exit
+
+EXAMPLE:
+
+  $ME --since=2008-01-01 > ChangeLog
+
+EOF
+    }
+  exit $exit_code;
+}
+
+# If the string $S is a well-behaved file name, simply return it.
+# If it contains white space, quotes, etc., quote it, and return the new 
string.
+sub shell_quote($)
+{
+  my ($s) = @_;
+  if ($s =~ m![^\w+/.,-]!)
+    {
+      # Convert each single quote to '\''
+      $s =~ s/\'/\'\\\'\'/g;
+      # Then single quote the string.
+      $s = "'$s'";
+    }
+  return $s;
+}
+
+sub quoted_cmd(@)
+{
+  return join (' ', map {shell_quote $_} @_);
+}
+
+{
+  my $since_date = '1970-01-01 UTC';
+  GetOptions
+    (
+     help => sub { usage 0 },
+     version => sub { print "$ME version $VERSION\n"; exit },
+     'since=s' => \$since_date,
+    ) or usage 1;
+
+  @ARGV
+    and (warn "$ME: too many arguments\n"), usage 1;
+
+  my @cmd = (qw (git log --log-size), "--since=$since_date",
+             '--pretty=format:%at  %an  <%ae>%n%n%s%n%b%n');
+  open PIPE, '-|', @cmd
+    or die "$ME: failed to run `". quoted_cmd (@cmd) ."': $!\n";
+
+  my $prev_date_line = '';
+  while (1)
+    {
+      defined (my $in = <PIPE>)
+        or last;
+      $in =~ /^log size (\d+)$/
+        or die "$ME:$.: Invalid line (expected log size):\n$in";
+      my $log_nbytes = $1;
+
+      my $log;
+      my $n_read = read PIPE, $log, $log_nbytes;
+      $n_read == $log_nbytes
+        or die "$ME:$.: unexpected EOF\n";
+
+      my @line = split "\n", $log;
+      my $author_line = shift @line;
+      defined $author_line
+        or die "$ME:$.: unexpected EOF\n";
+      $author_line =~ /^(\d+)  (.*>)$/
+        or die "$ME:$.: Invalid line "
+          . "(expected date/author/email):\n$author_line\n";
+
+      my $date_line = sprintf "%s  $2\n", strftime ("%F", localtime ($1));
+      # If this line would be the same as the previous date/name/email
+      # line, then arrange not to print it.
+      if ($date_line ne $prev_date_line)
+        {
+          $prev_date_line eq ''
+            or print "\n";
+          print $date_line;
+        }
+      $prev_date_line = $date_line;
+
+      # Omit "Signed-off-by..." lines.
+      @line = grep !/^Signed-off-by: .*>$/, @line;
+
+      # Remove leading and trailing blank lines.
+      while ($line[0] =~ /^\s*$/) { shift @line; }
+      while ($line[$#line] =~ /^\s*$/) { pop @line; }
+
+      # Prefix each non-empty line with a TAB.
+      @line = map { length $_ ? "\t$_" : '' } @line;
+
+      print "\n", join ("\n", @line), "\n";
+
+      defined ($in = <PIPE>)
+        or last;
+      $in ne "\n"
+        and die "$ME:$.: unexpected line:\n$in";
+    }
+
+  close PIPE
+    or die "$ME: error closing pipe from " . quoted_cmd (@cmd) . "\n";
+  # FIXME-someday: include $PROCESS_STATUS in the diagnostic
+}
+
+# Local Variables:
+# indent-tabs-mode: nil
+# eval: (add-hook 'write-file-hooks 'time-stamp)
+# time-stamp-start: "my $VERSION = '"
+# time-stamp-format: "%:y-%02m-%02d %02H:%02M"
+# time-stamp-time-zone: "UTC"
+# time-stamp-end: "'; # UTC"
+# End:
diff --git a/modules/gitlog-to-changelog b/modules/gitlog-to-changelog
new file mode 100644
index 0000000..4b40334
--- /dev/null
+++ b/modules/gitlog-to-changelog
@@ -0,0 +1,19 @@
+Description:
+Convert git log to ChangeLog
+
+Files:
+build-aux/gitlog-to-changelog
+
+Depends-on:
+
+configure.ac:
+
+Makefile.am:
+
+Include:
+
+License:
+GPLed build tool
+
+Maintainer:
+Jim Meyering
--
1.5.4.35.g3cfc