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   9                         <h1>Dscho's Git log</h1>
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  11                         <table width=400px bgcolor=#e0e0e0 border=0>
  12                         <tr><th>Table of contents:</th></tr>
  13                         <tr><td>
  14                         <p><ul>
  15                         <li><a href=#1242408298>15 May 2009 Wasting way too much time on msysGit</a>
  16                         <li><a href=#1241995759>11 May 2009 Working on jgit diff</a>
  17                         <li><a href=#1239975597>17 Apr 2009 No time for Git</a>
  18                         <li><a href=#1238970571>06 Apr 2009 How to recover from a hackathon</a>
  19                         <li><a href=#1236554268>09 Mar 2009 So, what is missing from my <i>rebase-i-p</i> branch?</a>
  20                         <li><a href=#1236479389>08 Mar 2009 New Git for Windows version</a>
  21                         <li><a href=#1235092615>20 Feb 2009 Code reviews</a>
  22                         <li><a href=#1234409395>12 Feb 2009 Interactive <i>rebase</i> just learnt a new command: <i>topic</i></a>
  23                         <li><a href=#1234320806>11 Feb 2009 Thunderbird, oh Thunderbird, you always make my small brain hurt</a>
  24                         <li><a href=#1234141489>09 Feb 2009 <i>format-patch --thread</i> and Alpine</a>
  25                         </ul></p>
  26                         <a href=dscho.git?a=blob_plain;hb=da892e0e981fc68e7c4b971fdbff389c65604cbf;f=index.html>Older posts</a>
  27                         </td></tr></table>
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  36                         <table width=400px bgcolor=#e0e0e0 border=0>
  37                         <tr><th>About this blog:</th></tr>
  38                         <tr><td>
  39                         <p>It is an active <a href=http://repo.or.cz/w/git/dscho.git?a=blob_plain;f=index.html;hb=5f002cab57a837125a8f901bcd1f3c1477bc3119>abuse</a> of <a href=http://repo.or.cz/>repo.or.cz</a>,
  40                         letting gitweb unpack the objects in the current tip of the branch <i>blog</i>,
  41                         including the images and the RSS feed.
  42                         </p><p>
  43                         Publishing means running a script that collects the posts, turns them into
  44                         HTML, makes sure all the images are checked in, and pushes the result.
  45                         </p><p>
  46                         This blog also serves to grace the world with Dscho's random thoughts on and
  47                         around Git.
  48                         </p>
  49                         </td></tr></table>
  50                         <br>
  51                         <table width=400px bgcolor=#e0e0e0 border=0>
  52                         <tr><th>Links:</th></tr>
  53                         <tr><td>
  54                         <ul>
  55                         <li> <a href=http://git-scm.com/>Git's homepage</a>
  56                         <li> <a href=http://gitster.livejournal.com/>Junio's blog</a>
  57                         <li> <a href=http://www.spearce.org/>Shawn's blog</a> seems to be sitting
  58                               idle ever since he started working for Google...
  59                         <li> <a href=http://torvalds-family.blogspot.com/>Linus' blog</a> does not
  60                               talk much about Git...
  61                         <li> Scott Chacon's <a href=http://whygitisbetterthanx.com/>Why Git is better
  62                              than X</a> site
  63                         <li> <a href=http://vilain.net/>The blog of mugwump</a>
  64                         <li> <a href=http://merlyn.vox.com/>Merlyn's blog</a>
  65                         <li> <a href=http://blogs.gnome.org/newren/>Elijah Newren</a> chose the
  66                               same path as Cogito, offering an alternative porcelain (an approach
  67                               that is doomed in my opinion)
  68                         <li> <a href=http://msysgit.googlecode.com/>The msysGit project</a>, a (mostly)
  69                               failed experiment to lure the many Windows developers out there to
  70                               contribute to Open Source for a change.
  71                         </ul>
  72                         </td></tr></table>
  73                         <br>
  74                         <table width=400px bgcolor=#e0e0e0 border=0>
  75                         <tr><th>Google Ads:</th></tr>
  76                         <tr><td>
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  89                         </div>
  90                         <h6>Friday, 15th of May, Anno Domini MMIX, at the hour of the Dog</h6>
  91                         <a name=1242408298>
  92                         <h2>Wasting way too much time on msysGit</h2>
  93
  94                         <p>
  95                         </p><p>
  96                         I recently got into the bad habit of spending a large amount of my waking
  97                         hours working on msysGit, more than is really healthy for me.
  98                         </p><p>
  99                         For example, I spent the whole morning -- when I should have worked on a
 100                         very important day-job project -- on trying to fix issue 258, where
 101                         <i>git web--browse</i> does not work as expected because of quoting issues
 102                         with cmd.exe.
 103                         </p><p>
 104                         This is reducing my Git time budget to negative numbers, so much so that I
 105                         cannot even work on Git projects that I actually like, such as <i>jgit diff</i>
 106                         or <i>git rebase -i -p</i>, or at least projects I felt obliged to continue
 107                         to work on, such as <i>git notes</i>.
 108                         </p><p>
 109                         Now, some people who tried to teach me some time management strongly
 110                         criticized me for ignoring their lessons, and unfortunately, I have to agree.
 111                         </p><p>
 112                         The problem is that I would <u>hate</u> to see msysGit fall to the same state it
 113                         was after I stopped working on it last year.  I started it, and I would like
 114                         it to grow, but too few people took care of the issue tracker, too few tried
 115                         to debug their problems themselves, too few submitted fixes.
 116                         </p><p>
 117                         I note, though, that there is a positive trend.  But being the impatient person
 118                         I am ("2 seconds is my attention span") I tend to want the trend to be more
 119                         impressive.
 120                         </p><p>
 121                         Anyway, no work on msysGit for at least 4 days, that's what the doctor (me)
 122                         said...
 123                         </p>
 124                         <h6>Monday, 11th of May, Anno Domini MMIX, at the hour of the Rat</h6>
 125                         <a name=1241995759>
 126                         <h2>Working on jgit diff</h2>
 127
 128                         <p>
 129                         </p><p>
 130                         Shawn did so many useful things that I use on a daily basis that I felt really
 131                         awful when I realized just how <u>long</u> I had promised to clean up that diff
 132                         implementation I wrote for JGit.
 133                         </p><p>
 134                         Alas, it appears that the thing turned out to be almost a complete rewrite, as
 135                         the original implementation walked the edit graph in a rather inefficient way.
 136                         </p><p>
 137                         A little background: Myers' algorithm to generate "an edit script" works on
 138                         the <i>edit graph</i>: imagine you have all lines of file <i>A</i> as columns and
 139                         all lines of file <i>B</i> as rows, then the <i>edit graph</i> is a connection of
 140                         the upper left corner to the lower right corner, containing only horizontal,
 141                         vertical or diagonal elements, where diagonal elements are only allowed when
 142                         the lines of both files agree at that point:
 143                         </p><p>
 144 <pre>
 145  H E L L O , W O R L D
 146  ----
 147 L    \
 148       ---
 149 O        \
 150           ---
 151 W            \
 152               --------
 153 </pre>
 154                         </p><p>
 155                         The <i>shortest</i> edit path minimizes the number of non-diagonal elements.
 156                         </p><p>
 157                         Myers' idea is to develop forward and backward paths at the same time
 158                         (increasing the number of non-diagonal elements uniformly), storing
 159                         only the latest end points.  Once the paths meet, divide and conquer.
 160                         </p><p>
 161                         In theory, it would be quicker to store <u>all</u> end points and then just
 162                         reconstruct the shortest paths, alas, this takes way too much memory.
 163                         </p><p>
 164                         My first implementation did not remember start or end of the non-diagonal
 165                         parts, and had to recurse way more often than really necessary (in the end,
 166                         we will order the non-diagonal parts into horizontal and vertical parts
 167                         anyway, so start and end are sufficient).
 168                         </p><p>
 169                         The current progress can be seen <a href=http://repo.or.cz/w/egit/dscho.git/>
 170                         here</a>.
 171                         </p>
 172                         <h6>Friday, 17th of April, Anno Domini MMIX, at the hour of the Monkey</h6>
 173                         <a name=1239975597>
 174                         <h2>No time for Git</h2>
 175
 176                         <p>
 177                         </p><p>
 178                         It is a shame, but most of my Git time budget is taken by msysGit these
 179                         days.
 180                         </p><p>
 181                         But at least msysGit is moving again; I'll probably write a Herald about
 182                         it.
 183                         </p>
 184                         <h6>Monday, 6th of April, Anno Domini MMIX, at the hour of the Rat</h6>
 185                         <a name=1238970571>
 186                         <h2>How to recover from a hackathon</h2>
 187
 188                         <p>
 189                         </p><p>
 190                         Phew, 2 crazy and fantastic weeks are behind me.  But it takes its toll:
 191                         a weekend I was more offline than online.
 192                         </p><p>
 193                         Things that are important now: relax. sleep. take a walk. learn to sleep
 194                         more than 4 hours a night again. learn to watch a movie without thinking
 195                         about code. go for a run.
 196                         </p><p>
 197                         And after recovering, back to the rebase-i-p branch!
 198                         </p>
 199                         <h6>Monday, 9th of March, Anno Domini MMIX, at the hour of the Rat</h6>
 200                         <a name=1236554268>
 201                         <h2>So, what is missing from my <i>rebase-i-p</i> branch?</h2>
 202
 203                         <p>
 204                         </p><p>
 205                         I regularly use <i>rebase -i -p</i> these days, to update my personal Git
 206                         tree (which used to be <i>my-next</i>).
 207                         </p><p>
 208                         There are a few things missing before I can start assembling a patch
 209                         series for submission:
 210                         </p><p>
 211                         <ul>
 212                         <li>I need to handle the commit parents which are outside of the rebased
 213                         ones properly.  In other words, when a commit is picked whose parent is
 214                         not rebased, it needs to be rebased onto $ONTO.
 215                         <li>The patch which uses patch-id to generate DROPPED directly also tries to
 216                         consolidate the handling of DROPPED commits by putting them into REWRITTEN
 217                         instead of DROPPED, but that breaks the tests.  So, this patch needs to be
 218                         split.
 219                         <li>I want to introduce one more command, <i>rephrase</i>, which allows you to
 220                         modify the commit message, and nothing more, and <i>halt</i>, which does the
 221                         same as <i>edit</i> without <i>pick</i>.  Then there needs to be a new test script
 222                         for those commands, and this will be an early patch series.
 223                         <li>Time.  I need time, desperately.  If my day job was not as exciting as it
 224                         is, I would have more time for Git.  As it is, I have to budget my time so
 225                         that I get anything done at all.
 226                         </ul>
 227                         </p><p>
 228                         These issues have been postponed due to Steffen taking a well-deserved
 229                         vacation, which means that I have to act as msysGit maintainer again.
 230                         </p><p>
 231                         And this coming week, I will have other things to do in all likeliness, so
 232                         that I expect to be able to submit a <i>rebase -i -p</i> patch series only next
 233                         week.  If not then, due to a heavy workload, it will be postponed to early
 234                         April.
 235                         </p><p>
 236                         Oh well, the joys of being excited by several competing projects! &#x263a;
 237                         </p>
 238                         <h6>Sunday, 8th of March, Anno Domini MMIX, at the hour of the Tiger</h6>
 239                         <a name=1236479389>
 240                         <h2>New Git for Windows version</h2>
 241
 242                         <p>
 243                         </p><p>
 244                         Phew.  That was quite a day, almost exclusively spent on finishing that
 245                         installer.  The worst part: updating GCC seemed not to be such a good idea
 246                         after all...
 247                         </p><p>
 248                         For Windows, we need to use the printf format <i>%I64u</i> (which is
 249                         non-standard, in the common way of Microsoft) if you want to print 64-bit
 250                         wide unsigned numbers.  The rest of the world accepts the standard <i>%llu</i>.
 251                         </p><p>
 252                         After upgrading to the new GCC, a lot of warnings appeared, complaining
 253                         about <i>%I64u</i>.  The warnings went away when I replaced the format with
 254                         <i>%llu</i>.
 255                         </p><p>
 256                         Being the naive I am, I mistook that for a sign that we could finally go
 257                         more standards-compliant.
 258                         </p><p>
 259                         However, it only means that we have to live with the warnings for now, as
 260                         the C runtime provided on Windows still strongly disagrees with standards
 261                         (and it has to continue to do so, lest it break existing programs).
 262                         </p><p>
 263                         Sigh.
 264                         </p><p>
 265                         At least I have the feeling that I caught the most important bugs before
 266                         releasing.
 267                         </p>
 268                         <h6>Friday, 20th of February, Anno Domini MMIX, at the hour of the Buffalo</h6>
 269                         <a name=1235092615>
 270                         <h2>Code reviews</h2>
 271
 272                         <p>
 273                         </p><p>
 274                         It has been said that reviewing patches is a most thankless job.  As I really
 275                         like the elegance of Git's source code, and care a lot about it, I did not
 276                         think that it was thankless, just a little bit tedious (especially when the
 277                         patch authors mistake criticism for personal attacks).
 278                         </p><p>
 279                         Usually, I am pretty good at ignoring insults as responses to my comments;
 280                         after all, I have a lot more enjoyable things to do than to spend time talking
 281                         to a guy who shows how wise he is when he thinks that I criticize him
 282                         <u>personally</u> when I just try to enhance his work, by offering a little bit of
 283                         my knowledge.
 284                         </p><p>
 285                         However, in the last days, three people really seemed to want to insult me,
 286                         to make me go away, to stop the fun I have with Git.
 287                         </p><p>
 288                         And they almost succeeded.
 289                         </p><p>
 290                         So I guess it is time to reassess my priorities, and maybe stop reviewing
 291                         Git patches altogether.
 292                         </p>
 293                         <h6>Thursday, 12th of February, Anno Domini MMIX, at the hour of the Tiger</h6>
 294                         <a name=1234409395>
 295                         <h2>Interactive <i>rebase</i> just learnt a new command: <i>topic</i></h2>
 296
 297                         <p>
 298                         </p><p>
 299                         Today I am pretty pleased with myself.  Two projects at my day job got a real
 300                         boost, and I implemented a shortcut that avoids the ugly 'bookmark' statement
 301                         in rebase scripts most of the time.
 302                         </p><p>
 303                         A typical rebase script, generated by <i>git rebase -i -p $COMMIT</i> will look
 304                         something like this:
 305                         </p><p>
 306                         <table
 307                                                         border=1 bgcolor=black>
 308                                                 <tr><td bgcolor=lightblue colspan=3>
 309                                 <pre>                                                                                </pre>
 310                         </td></tr>
 311                         <tr><td>
 312                                 <table cellspacing=5 border=0
 313                                          style="color:white;">
 314                                 <tr><td>
 315                                         <pre>
 316 pick 1234567 My first commit
 317 topic begin super-cool-feature
 318 pick 2345678 The super cool feature
 319 pick 3456789 Documentation for the super cool feature
 320 topic end super-cool-feature
 321 </pre>
 322                                                         </td></tr>
 323                                                         </table>
 324                                                 </td></tr>
 325                                                 </table>
 326                         </p><p>
 327                         The result will be a merge commit at the HEAD whose first parent is
 328                         "My first commit", whose second parent is "Documentation for the super
 329                         cool feature" and whose commit message is "Merge branch 'super-cool-feature'".
 330                         </p><p>
 331                         Side note: internally, <i>topic begin $NAME [at $COMMIT]</i> will be handled as if
 332                         you wrote <i>bookmark merge-parent-of-$NAME; goto $COMMIT</i>, and
 333                         <i>topic end $NAME [$MESSAGE]</i> will be handled as if you wrote
 334                         <i>bookmark $NAME; goto merge-parent-of-$NAME; merge parents $NAME [original $MARK Merge branch '$NAME']</i>.
 335                         </p><p>
 336                         Of course, being more concise, the 'topic' statement is not only nicer to the
 337                         eye, but also less error-prone.
 338                         </p><p>
 339                         And hopefully many people will agree with me that this rebase script is pretty
 340                         intuitive.
 341                         </p>
 342                         <h6>Wednesday, 11th of February, Anno Domini MMIX, at the hour of the Tiger</h6>
 343                         <a name=1234320806>
 344                         <h2>Thunderbird, oh Thunderbird, you always make my small brain hurt</h2>
 345
 346                         <p>
 347                         </p><p>
 348                         There was a lengthy discussion on the Git mailing list about using Thunderbird,
 349                         a not quite unpopular mailing program, to send inline patches.
 350                         </p><p>
 351                         It is really kind of sad that the Thunderbird developers do not see how
 352                         stubbornly they offend quite a number of people and scare them away from their
 353                         program.  After all, you should try to be liberal in what you accept and strict
 354                         in what you emit.  No, that does not mean that you should force others to
 355                         switch their mailers because you strictly adher to your philosophy in what you
 356                         emit, ignoring the rest of the world.
 357                         </p><p>
 358                         In any case, I am not affected (as long as I do not get mails from a poor soul
 359                         stuck with Thunderbird).
 360                         </p><p>
 361                         But I was a bit mean to that Thunderbird guy I dragged into the discussion, and
 362                         he seems really offended.
 363                         </p><p>
 364                         So I thought I'd give him a real reason to feel offended: I'll just do his work:
 365                         </p><p>
 366                         http://repo.or.cz/w/UnFlowedThunderbird.git
 367                         </p><p>
 368                         It took my free time of two days, being not a Thunderbird developer myself.
 369                         Hopefully it works, and hopefully some people will feel really ashamed now.
 370                         </p>
 371                         <h6>Monday, 9th of February, Anno Domini MMIX, at the hour of the Buffalo</h6>
 372                         <a name=1234141489>
 373                         <h2><i>format-patch --thread</i> and Alpine</h2>
 374
 375                         <p>
 376                         </p><p>
 377                         I started recently to pipe the output of
 378                         <i>git format-patch --cover-letter --stdout ...</i> directly into the
 379                         <i>postponed-msgs</i> folder Alpine uses, instead of pasting files into the
 380                         mailer.
 381                         </p><p>
 382                         The idea is to pretend that I continue a postponed mail, but in reality I
 383                         never wrote it, <i>format-patch</i> did.
 384                         </p><p>
 385                         However, I had problems with the <i>--thread</i> option that is implied by
 386                         <i>--cover-letter</i>.  Alpine always generated new message IDs without adjusting
 387                         the <i>In-reply-to:</i> and <i>References:</i> headers of the other mails.
 388                         </p><p>
 389                         Now I found out that the reason is that the <i>Fcc:</i> headers were missing in
 390                         the mails, and Alpine generated them, making up new message IDs in the process.
 391                         </p><p>
 392                         Therefore I have an alias now which sets not only the <i>Fcc:</i> header, but also
 393                         the <i>To:</i> headers by rewriting the stream using <i>sed</i>.  This is slightly
 394                         ugly, but so is the handling of headers in <i>format-patch</i>: if you thought
 395                         you could specify arbitrary headers using the command line, you are mistaken:
 396                         you can do that only by editing the config.
 397                         </p><p>
 398                         While at it, I also noticed a bug whereby <i>--thread --in-reply-to=...</i> simply
 399                         forgets the <i>--thread</i>.  Maybe this week I will find time to address this bug.
 400                         </p>
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