Improve git_changelog as per discussion with Robert Haas.

1. Resurrect the behavior where old commits on master will have Branch:
labels for branches sprouted after the commit was made.  I'm still
dubious about this mode, but if you want it, say --post-date or -p.

2. Annotate the Branch: labels with the release or branch in which the
commit was publicly released.  For example, on a release branch you could
see
Branch: REL8_3_STABLE Release: REL8_3_2 [92c3a80] 2008-03-29 00:15:37 +0000
showing that the fix was released in 8.3.2.  Commits on master will
usually instead have notes like
Branch: master Release: REL8_4_BR [6fc9d42] 2008-03-29 00:15:28 +0000
showing that this commit is ancestral to release branches 8.4 and later.
If no Release: marker appears, the commit hasn't yet made it into any
release.

3. Add support for release branches older than 7.4.

4. The implementation is improved by running git log on each branch only
back to where the branch sprouts from master.  This saves a good deal
of time (about 50% of the runtime when generating the complete history).
We generate the post-date-mode tags via a direct understanding that
they should be applied to master commits made before the branch sprouted,
rather than backing into them via matching (which isn't any too
reliable when people used identical log messages for successive commits).

Author: tglsfdc

src/tools/git_changelog

@@ -5,7 +5,14 @@
 #
 # Display all commits on active branches, merging together commits from
 # different branches that occur close together in time and with identical
-# log messages.
+# log messages.  Commits are annotated with branch and release info thus:
+# Branch: REL8_3_STABLE Release: REL8_3_2 [92c3a8004] 2008-03-29 00:15:37 +0000
+# This shows that the commit on REL8_3_STABLE was released in 8.3.2.
+# Commits on master will usually instead have notes like
+# Branch: master Release: REL8_4_BR [6fc9d4272] 2008-03-29 00:15:28 +0000
+# showing that this commit is ancestral to release branches 8.4 and later.
+# If no Release: marker appears, the commit hasn't yet made it into any
+# release.
 #
 # Most of the time, matchable commits occur in the same order on all branches,
 # and we print them out in that order.  However, if commit A occurs before
@@ -26,36 +33,84 @@ require Time::Local;
 require Getopt::Long;
 require IPC::Open2;
 
-# Adjust this list when the set of active branches changes.
+# Adjust this list when the set of interesting branches changes.
+# (We could get this from "git branches", but not worth the trouble.)
+# NB: master must be first!
 my @BRANCHES = qw(master REL9_0_STABLE REL8_4_STABLE REL8_3_STABLE
-    REL8_2_STABLE REL8_1_STABLE REL8_0_STABLE REL7_4_STABLE);
+    REL8_2_STABLE REL8_1_STABLE REL8_0_STABLE REL7_4_STABLE REL7_3_STABLE
+    REL7_2_STABLE REL7_1_STABLE REL7_0_PATCHES REL6_5_PATCHES REL6_4);
 
 # Might want to make this parameter user-settable.
 my $timestamp_slop = 600;
 
+my $post_date = 0;
 my $since;
-Getopt::Long::GetOptions('since=s' => \$since) || usage();
+Getopt::Long::GetOptions('post-date' => \$post_date,
+                         'since=s' => \$since) || usage();
 usage() if @ARGV;
 
 my @git = qw(git log --date=iso);
 push @git, '--since=' . $since if defined $since;
 
+# Collect the release tag data
+my %rel_tags;
+
+{
+	my $cmd = "git for-each-ref refs/tags";
+	my $pid = IPC::Open2::open2(my $git_out, my $git_in, $cmd)
+		|| die "can't run $cmd: $!";
+	while (my $line = <$git_out>) {
+		if ($line =~ m|^([a-f0-9]+)\s+commit\s+refs/tags/(\S+)|) {
+		    my $commit = $1;
+		    my $tag = $2;
+		    if ($tag =~ /^REL\d+_\d+$/ ||
+			$tag =~ /^REL\d+_\d+_\d+$/) {
+			$rel_tags{$commit} = $tag;
+		    }
+		}
+	}
+	waitpid($pid, 0);
+	my $child_exit_status = $? >> 8;
+	die "$cmd failed" if $child_exit_status != 0;
+}
+
+# Collect the commit data
 my %all_commits;
 my %all_commits_by_branch;
+# This remembers where each branch sprouted from master.  Note the values
+# will be wrong if --since terminates the log listing before the branch
+# sprouts; but in that case it doesn't matter since we also won't reach
+# the part of master where it would matter.
+my %sprout_tags;
 
 for my $branch (@BRANCHES) {
-	my $pid =
-	  IPC::Open2::open2(my $git_out, my $git_in, @git, "origin/$branch")
-	      || die "can't run @git origin/$branch: $!";
+	my @cmd = @git;
+	if ($branch eq "master") {
+	    push @cmd, "origin/$branch";
+	} else {
+	    push @cmd, "--parents";
+	    push @cmd, "master..origin/$branch";
+	}
+	my $pid = IPC::Open2::open2(my $git_out, my $git_in, @cmd)
+		|| die "can't run @cmd: $!";
+	my $last_tag = undef;
+	my $last_parent;
 	my %commit;
 	while (my $line = <$git_out>) {
-		if ($line =~ /^commit\s+(.*)/) {
+		if ($line =~ /^commit\s+(\S+)/) {
 			push_commit(\%commit) if %commit;
+			$last_tag = $rel_tags{$1} if defined $rel_tags{$1};
 			%commit = (
 				'branch' => $branch,
 				'commit' => $1,
+				'last_tag' => $last_tag,
 				'message' => '',
 			);
+			if ($line =~ /^commit\s+\S+\s+(\S+)/) {
+				$last_parent = $1;
+			} else {
+				$last_parent = undef;
+			}
 		}
 		elsif ($line =~ /^Author:\s+(.*)/) {
 			$commit{'author'} = $1;
@@ -68,9 +123,43 @@ for my $branch (@BRANCHES) {
 		}
 	}
 	push_commit(\%commit) if %commit;
+	$sprout_tags{$last_parent} = $branch if defined $last_parent;
 	waitpid($pid, 0);
 	my $child_exit_status = $? >> 8;
-	die "@git origin/$branch failed" if $child_exit_status != 0;
+	die "@cmd failed" if $child_exit_status != 0;
+}
+
+# Run through the master branch and apply tags.  We already tagged the other
+# branches, but master needs a separate pass after we've acquired the
+# sprout_tags data.  Also, in post-date mode we need to add phony entries
+# for branches that sprouted after a particular master commit was made.
+{
+	my $last_tag = undef;
+	my %sprouted_branches;
+	for my $cc (@{$all_commits_by_branch{'master'}}) {
+	    my $commit = $cc->{'commit'};
+	    my $c = $cc->{'commits'}->[0];
+	    $last_tag = $rel_tags{$commit} if defined $rel_tags{$commit};
+	    if (defined $sprout_tags{$commit}) {
+		$last_tag = $sprout_tags{$commit};
+		# normalize branch names for making sprout tags
+		$last_tag =~ s/^(REL\d+_\d+).*/$1_BR/;
+	    }
+	    $c->{'last_tag'} = $last_tag;
+	    if ($post_date) {
+		if (defined $sprout_tags{$commit}) {
+		    $sprouted_branches{$sprout_tags{$commit}} = 1;
+		}
+		# insert new commits between master and any other commits
+		my @new_commits = ( shift @{$cc->{'commits'}} );
+		for my $branch (reverse sort keys %sprouted_branches) {
+		    my $ccopy = {%{$c}};
+		    $ccopy->{'branch'} = $branch;
+		    push @new_commits, $ccopy;
+		}
+		$cc->{'commits'} = [ @new_commits, @{$cc->{'commits'}} ];
+	    }
+	}
 }
 
 my %position;
@@ -104,7 +193,14 @@ while (1) {
 	last if !defined $best_branch;
 	my $winner =
 		$all_commits_by_branch{$best_branch}->[$position{$best_branch}];
-	print $winner->{'header'};
+	printf "Author: %s\n", $winner->{'author'};
+	foreach my $c (@{$winner->{'commits'}}) {
+	    printf "Branch: %s", $c->{'branch'};
+	    if (defined $c->{'last_tag'}) {
+		printf " Release: %s", $c->{'last_tag'};
+	    }
+	    printf " [%s] %s\n", substr($c->{'commit'}, 0, 9), $c->{'date'};
+	}
 	print "Commit-Order-Inversions: $best_inversions\n"
 		if $best_inversions != 0;
 	print "\n";
@@ -143,22 +239,22 @@ sub push_commit {
 	}
 	if (!defined $cc) {
 		$cc = {
-			'header' => sprintf("Author: %s\n", $c->{'author'}),
+			'author' => $c->{'author'},
 			'message' => $c->{'message'},
 			'commit' => $c->{'commit'},
+			'commits' => [],
 			'timestamp' => $ts
 		};
 		push @{$all_commits{$ht}}, $cc;
-	} elsif ($cc->{'commit'} eq $c->{'commit'}) {
-	    # If this is exactly the same commit we saw before on another
-	    # branch, ignore it.  Hence, a commit that's reachable from more
-	    # than one branch head will be reported only for the first
-	    # head it's reachable from.  This will give the desired results
-	    # so long as @BRANCHES is ordered with master first.
-	    return;
 	}
-	$cc->{'header'} .= sprintf "Branch: %s [%s] %s\n",
-		$c->{'branch'}, substr($c->{'commit'}, 0, 9), $c->{'date'};
+	# stash only the fields we'll need later
+	my $smallc = {
+	    'branch' => $c->{'branch'},
+	    'commit' => $c->{'commit'},
+	    'date' => $c->{'date'},
+	    'last_tag' => $c->{'last_tag'}
+	};
+	push @{$cc->{'commits'}}, $smallc;
 	push @{$all_commits_by_branch{$c->{'branch'}}}, $cc;
 	$cc->{'branch_position'}{$c->{'branch'}} =
 		-1+@{$all_commits_by_branch{$c->{'branch'}}};
@@ -180,7 +276,9 @@ sub parse_datetime {
 
 sub usage {
 	print STDERR <<EOM;
-Usage: git_changelog [--since=SINCE]
+Usage: git_changelog [--post-date/-p] [--since=SINCE]
+    --post-date Show branches made after a commit occurred
+    --since     Print only commits dated since SINCE
 EOM
 	exit 1;
 }