X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/a8e3040d0aa6c717bec072bff9cd80223e399a0c..651cdd4b2a85f4e5f9d298a7eea7d0e6d94442b1:/doc/todo/headless_git_branches.mdwn diff --git a/doc/todo/headless_git_branches.mdwn b/doc/todo/headless_git_branches.mdwn index 8a1e68201..d9bb38099 100644 --- a/doc/todo/headless_git_branches.mdwn +++ b/doc/todo/headless_git_branches.mdwn @@ -6,46 +6,162 @@ Ikiwiki should really survive being asked to work with a git branch that has no git clone barerepo.git srcdir ikiwiki --rcs=git srcdir destdir -I've fixed this initial construction case, and, based on my testing, I've also fixed the post-update executing on a new master, and ikiwiki.cgi executing on a non-existent master cases. Unfortunately these cases still generate a lot of warnings from recentchanges; I suspect a much more invasive patch would be needed to shut those up. +I've fixed this initial construction case, and, based on my testing, I've +also fixed the post-update executing on a new master, and ikiwiki.cgi +executing on a non-existent master cases. Please commit so my users stop whining at me about having clean branches to push to, the big babies. -Summary: Change three scary loud failure cases related to empty branches into three scary loud success cases. +Summary: Change three scary loud failure cases related to empty branches into three mostly quiet success cases. + +[[!tag patch]] + +> FWIW, [[The_TOVA_Company]] apparently wants this feature (and I hope +> I don't mind that I mention they were willing to pay someone for it, +> but I told them I'd not done any of the work. :) ) +> +> Code review follows, per hunk.. --[[Joey]] +
diff --git a/IkiWiki/Plugin/git.pm b/IkiWiki/Plugin/git.pm -index cf7fbe9..5b1e334 100644 +index cf7fbe9..e5bafcf 100644 --- a/IkiWiki/Plugin/git.pm +++ b/IkiWiki/Plugin/git.pm -@@ -439,10 +439,13 @@ sub git_commit_info ($;$) { +@@ -439,17 +439,21 @@ sub git_commit_info ($;$) { my @opts; push @opts, "--max-count=$num" if defined $num; -+ my @raw_lines; - +- - my @raw_lines = run_or_die('git', 'log', @opts, - '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c', - '-r', $sha1, '--', '.'); -+ if (-e $config{srcdir} . "/.git/refs/heads/" . $config{gitmaster_branch}) { -+ @raw_lines = run_or_die('git', 'log', @opts, -+ '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c', -+ '-r', $sha1, '--', '.'); -+ }; - +- ++ my @raw_lines; my @ci; - while (my $parsed = parse_diff_tree(\@raw_lines)) { -@@ -474,7 +477,10 @@ sub rcs_update () { +- while (my $parsed = parse_diff_tree(\@raw_lines)) { +- push @ci, $parsed; +- } ++ ++ # Test to see if branch actually exists yet. ++ if (run_or_non('git', 'show-ref', '--quiet', '--verify', '--', 'refs/heads/' . $config{gitmaster_branch}) ) { ++ @raw_lines = run_or_die('git', 'log', @opts, ++ '--pretty=raw', '--raw', '--abbrev=40', '--always', '-c', ++ '-r', $sha1, '--', '.'); ++ ++ while (my $parsed = parse_diff_tree(\@raw_lines)) { ++ push @ci, $parsed; ++ } + +- warn "Cannot parse commit info for '$sha1' commit" if !@ci; ++ warn "Cannot parse commit info for '$sha1' commit" if !@ci; ++ }; + + return wantarray ? @ci : $ci[0]; + } ++ +My concern is that this adds a bit of slowdown (git show-ref is fast, but +It's still extra work) to a very hot code path that is run to eg, +update recentchanges after every change. + +Seems not ideal to do extra work every time to handle a case +that will literally happen a maximum of once in the entire lifecycle of a +wiki (and zero times more typically, since the setup automator puts in a +.gitignore file that works around this problem). + +So as to not just say "no" ... what if it always tried to run git log, +and if it failed (or returned no parsed lines), then it could look +at git show-ref to deduce whether to throw an error or not. +--[[Joey]] + +> Ah, but then git-log would still complain "bad revision 'HEAD'" +> --[[Joey]] + + jrayhawk@piny:/srv/git/jrayhawk.git$ time perl -e 'for( $i = 1; $i < 10000; $i++) { system("git", "show-ref", "--quiet", "--verify", "--", "refs/heads/master"); }' + + real 0m10.988s + user 0m0.120s + sys 0m1.210s + +> FWIW, "an extra millisecond per edit" vs "full git coverage" is no +> contest for me; I use that patch on seven different systems, including +> freedesktop.org, because I've spent more time explaining to users either +> why Ikiwiki won't work on their empty repositories or why their +> repositories need useless initial commits (a la Branchable) that make +> pushing not work and why denyNonFastForwards=0 and git push -f are +> necessary than all the milliseconds that could've been saved in the +> world. +> +> But, since we're having fun rearranging deck chairs on the RMS Perl +> (toot toot)... +> +> There's some discrepency here I wasn't expecting: + + jrayhawk@piny:/srv/git/jrayhawk.git$ time dash -c 'i=0; while [ $i -lt 10000 ]; do i=$((i+1)); git show-ref --quiet --verify -- refs/heads/master; done' + + real 0m9.986s + user 0m0.170s + sys 0m0.940s + +> While looking around in the straces, I notice Perl, unlike {b,d}ash +> appears to do PATH lookup on every invocation of git, adding up to +> around 110 microseconds apiece on a post-2.6.38 16-thread QPI system: + + 29699 0.000112 execve("/home/jrayhawk/bin/git", ["git", "show-ref", "--quiet", "--verify", "--", "refs/heads/master"], [/* 17 vars */]) = -1 ENOENT (No such file or directory) + 29699 0.000116 execve("/usr/local/bin/git", ["git", "show-ref", "--quiet", "--verify", "--", "refs/heads/master"], [/* 17 vars */]) = -1 ENOENT (No such file or directory) + 29699 0.000084 execve("/usr/bin/git", ["git", "show-ref", "--quiet", "--verify", "--", "refs/heads/master"], [/* 17 vars */]) = 0 + +> You can probably save a reasonable number of context switches and +> RCU-heavy (or, previously, lock-heavy) dentry lookups by doing a Perl +> equivalent of `which git` and using the result. It might even add up to +> a whole millisecond in some circumstances! +> +> No idea where the rest of that time is going. Probably cache misses +> on the giant Perl runtime or something. +> +> ... +> +> Now I feel dirty for having spent more time talking about optimization +> than that optimization is likely to save. This must be what being an +> engineer feels like. +> --jrayhawk + +
+@@ -474,7 +478,10 @@ sub rcs_update () { # Update working directory. if (length $config{gitorigin_branch}) { - run_or_cry('git', 'pull', '--prune', $config{gitorigin_branch}); -+ run_or_cry('git', 'fetch', '--prune', $config{gitorigin_branch}); -+ if (-e $config{srcdir} . '/.git/refs/remotes/' . $config{gitorigin_branch} . '/' . $config{gitmaster_branch}) { -+ run_or_cry('git', 'merge', $config{gitorigin_branch} . '/' . $config{gitmaster_branch}); -+ } ++ run_or_cry('git', 'fetch', '--prune', $config{gitorigin_branch}); ++ if (run_or_non('git', 'show-ref', '--quiet', '--verify', '--', 'refs/remotes/' . $config{gitorigin_branch} . '/' . $config{gitmaster_branch}) ) { ++ run_or_cry('git', 'merge', $config{gitorigin_branch} . '/' . $config{gitmaster_branch}); ++ } } } - -@@ -559,7 +565,7 @@ sub rcs_commit_helper (@) { + ++ +Same concern here about extra work. Code path is nearly as hot, being +called on every refresh. Probably could be dealt with similarly as above. + +Also, is there any point in breaking the pull up into a +fetch followed by a merge? --[[Joey]] + +> The same benchmarking applies, at least. +> +> Re: fetch/merge: We can't test for the nonexistence of the origin branch +> without fetching it, and we can't merge it if it is, indeed, +> nonexistant. +> +> Unless you're implying that it would be better to just spam stderr with +> unnecessary scary messages and/or ignore/suppress them and lose the +> ability to respond appropriately to every other error condition. As +> maintainer, you deal with a disproportionate amount of the resulting +> support fallout, so I'm perfectly satisfied letting you make that call. +> --jrayhawk + +
+@@ -559,7 +566,7 @@ sub rcs_commit_helper (@) { # So we should ignore its exit status (hence run_or_non). if (run_or_non('git', 'commit', '-m', $params{message}, '-q', @opts)) { if (length $config{gitorigin_branch}) { @@ -53,4 +169,10 @@ index cf7fbe9..5b1e334 100644 + run_or_cry('git', 'push', $config{gitorigin_branch}, $config{gitmaster_branch}); } } ++ +This seems fine to apply. --[[Joey]] + +> Hooray! +> --jrayhawk