howto/recover-corrupted-blob-object.html

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
   3     "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
   4 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
   5 <head>
   6 <meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
   7 <meta name="generator" content="AsciiDoc 10.2.0" />
   8 <title>How to recover a corrupted blob object</title>
   9 <style type="text/css">
  10 /* Shared CSS for AsciiDoc xhtml11 and html5 backends */
  11
  12 /* Default font. */
  13 body {
  14   font-family: Georgia,serif;
  15 }
  16
  17 /* Title font. */
  18 h1, h2, h3, h4, h5, h6,
  19 div.title, caption.title,
  20 thead, p.table.header,
  21 #toctitle,
  22 #author, #revnumber, #revdate, #revremark,
  23 #footer {
  24   font-family: Arial,Helvetica,sans-serif;
  25 }
  26
  27 body {
  28   margin: 1em 5% 1em 5%;
  29 }
  30
  31 a {
  32   color: blue;
  33   text-decoration: underline;
  34 }
  35 a:visited {
  36   color: fuchsia;
  37 }
  38
  39 em {
  40   font-style: italic;
  41   color: navy;
  42 }
  43
  44 strong {
  45   font-weight: bold;
  46   color: #083194;
  47 }
  48
  49 h1, h2, h3, h4, h5, h6 {
  50   color: #527bbd;
  51   margin-top: 1.2em;
  52   margin-bottom: 0.5em;
  53   line-height: 1.3;
  54 }
  55
  56 h1, h2, h3 {
  57   border-bottom: 2px solid silver;
  58 }
  59 h2 {
  60   padding-top: 0.5em;
  61 }
  62 h3 {
  63   float: left;
  64 }
  65 h3 + * {
  66   clear: left;
  67 }
  68 h5 {
  69   font-size: 1.0em;
  70 }
  71
  72 div.sectionbody {
  73   margin-left: 0;
  74 }
  75
  76 hr {
  77   border: 1px solid silver;
  78 }
  79
  80 p {
  81   margin-top: 0.5em;
  82   margin-bottom: 0.5em;
  83 }
  84
  85 ul, ol, li > p {
  86   margin-top: 0;
  87 }
  88 ul > li     { color: #aaa; }
  89 ul > li > * { color: black; }
  90
  91 .monospaced, code, pre {
  92   font-family: "Courier New", Courier, monospace;
  93   font-size: inherit;
  94   color: navy;
  95   padding: 0;
  96   margin: 0;
  97 }
  98 pre {
  99   white-space: pre-wrap;
 100 }
 101
 102 #author {
 103   color: #527bbd;
 104   font-weight: bold;
 105   font-size: 1.1em;
 106 }
 107 #email {
 108 }
 109 #revnumber, #revdate, #revremark {
 110 }
 111
 112 #footer {
 113   font-size: small;
 114   border-top: 2px solid silver;
 115   padding-top: 0.5em;
 116   margin-top: 4.0em;
 117 }
 118 #footer-text {
 119   float: left;
 120   padding-bottom: 0.5em;
 121 }
 122 #footer-badges {
 123   float: right;
 124   padding-bottom: 0.5em;
 125 }
 126
 127 #preamble {
 128   margin-top: 1.5em;
 129   margin-bottom: 1.5em;
 130 }
 131 div.imageblock, div.exampleblock, div.verseblock,
 132 div.quoteblock, div.literalblock, div.listingblock, div.sidebarblock,
 133 div.admonitionblock {
 134   margin-top: 1.0em;
 135   margin-bottom: 1.5em;
 136 }
 137 div.admonitionblock {
 138   margin-top: 2.0em;
 139   margin-bottom: 2.0em;
 140   margin-right: 10%;
 141   color: #606060;
 142 }
 143
 144 div.content { /* Block element content. */
 145   padding: 0;
 146 }
 147
 148 /* Block element titles. */
 149 div.title, caption.title {
 150   color: #527bbd;
 151   font-weight: bold;
 152   text-align: left;
 153   margin-top: 1.0em;
 154   margin-bottom: 0.5em;
 155 }
 156 div.title + * {
 157   margin-top: 0;
 158 }
 159
 160 td div.title:first-child {
 161   margin-top: 0.0em;
 162 }
 163 div.content div.title:first-child {
 164   margin-top: 0.0em;
 165 }
 166 div.content + div.title {
 167   margin-top: 0.0em;
 168 }
 169
 170 div.sidebarblock > div.content {
 171   background: #ffffee;
 172   border: 1px solid #dddddd;
 173   border-left: 4px solid #f0f0f0;
 174   padding: 0.5em;
 175 }
 176
 177 div.listingblock > div.content {
 178   border: 1px solid #dddddd;
 179   border-left: 5px solid #f0f0f0;
 180   background: #f8f8f8;
 181   padding: 0.5em;
 182 }
 183
 184 div.quoteblock, div.verseblock {
 185   padding-left: 1.0em;
 186   margin-left: 1.0em;
 187   margin-right: 10%;
 188   border-left: 5px solid #f0f0f0;
 189   color: #888;
 190 }
 191
 192 div.quoteblock > div.attribution {
 193   padding-top: 0.5em;
 194   text-align: right;
 195 }
 196
 197 div.verseblock > pre.content {
 198   font-family: inherit;
 199   font-size: inherit;
 200 }
 201 div.verseblock > div.attribution {
 202   padding-top: 0.75em;
 203   text-align: left;
 204 }
 205 /* DEPRECATED: Pre version 8.2.7 verse style literal block. */
 206 div.verseblock + div.attribution {
 207   text-align: left;
 208 }
 209
 210 div.admonitionblock .icon {
 211   vertical-align: top;
 212   font-size: 1.1em;
 213   font-weight: bold;
 214   text-decoration: underline;
 215   color: #527bbd;
 216   padding-right: 0.5em;
 217 }
 218 div.admonitionblock td.content {
 219   padding-left: 0.5em;
 220   border-left: 3px solid #dddddd;
 221 }
 222
 223 div.exampleblock > div.content {
 224   border-left: 3px solid #dddddd;
 225   padding-left: 0.5em;
 226 }
 227
 228 div.imageblock div.content { padding-left: 0; }
 229 span.image img { border-style: none; vertical-align: text-bottom; }
 230 a.image:visited { color: white; }
 231
 232 dl {
 233   margin-top: 0.8em;
 234   margin-bottom: 0.8em;
 235 }
 236 dt {
 237   margin-top: 0.5em;
 238   margin-bottom: 0;
 239   font-style: normal;
 240   color: navy;
 241 }
 242 dd > *:first-child {
 243   margin-top: 0.1em;
 244 }
 245
 246 ul, ol {
 247     list-style-position: outside;
 248 }
 249 ol.arabic {
 250   list-style-type: decimal;
 251 }
 252 ol.loweralpha {
 253   list-style-type: lower-alpha;
 254 }
 255 ol.upperalpha {
 256   list-style-type: upper-alpha;
 257 }
 258 ol.lowerroman {
 259   list-style-type: lower-roman;
 260 }
 261 ol.upperroman {
 262   list-style-type: upper-roman;
 263 }
 264
 265 div.compact ul, div.compact ol,
 266 div.compact p, div.compact p,
 267 div.compact div, div.compact div {
 268   margin-top: 0.1em;
 269   margin-bottom: 0.1em;
 270 }
 271
 272 tfoot {
 273   font-weight: bold;
 274 }
 275 td > div.verse {
 276   white-space: pre;
 277 }
 278
 279 div.hdlist {
 280   margin-top: 0.8em;
 281   margin-bottom: 0.8em;
 282 }
 283 div.hdlist tr {
 284   padding-bottom: 15px;
 285 }
 286 dt.hdlist1.strong, td.hdlist1.strong {
 287   font-weight: bold;
 288 }
 289 td.hdlist1 {
 290   vertical-align: top;
 291   font-style: normal;
 292   padding-right: 0.8em;
 293   color: navy;
 294 }
 295 td.hdlist2 {
 296   vertical-align: top;
 297 }
 298 div.hdlist.compact tr {
 299   margin: 0;
 300   padding-bottom: 0;
 301 }
 302
 303 .comment {
 304   background: yellow;
 305 }
 306
 307 .footnote, .footnoteref {
 308   font-size: 0.8em;
 309 }
 310
 311 span.footnote, span.footnoteref {
 312   vertical-align: super;
 313 }
 314
 315 #footnotes {
 316   margin: 20px 0 20px 0;
 317   padding: 7px 0 0 0;
 318 }
 319
 320 #footnotes div.footnote {
 321   margin: 0 0 5px 0;
 322 }
 323
 324 #footnotes hr {
 325   border: none;
 326   border-top: 1px solid silver;
 327   height: 1px;
 328   text-align: left;
 329   margin-left: 0;
 330   width: 20%;
 331   min-width: 100px;
 332 }
 333
 334 div.colist td {
 335   padding-right: 0.5em;
 336   padding-bottom: 0.3em;
 337   vertical-align: top;
 338 }
 339 div.colist td img {
 340   margin-top: 0.3em;
 341 }
 342
 343 @media print {
 344   #footer-badges { display: none; }
 345 }
 346
 347 #toc {
 348   margin-bottom: 2.5em;
 349 }
 350
 351 #toctitle {
 352   color: #527bbd;
 353   font-size: 1.1em;
 354   font-weight: bold;
 355   margin-top: 1.0em;
 356   margin-bottom: 0.1em;
 357 }
 358
 359 div.toclevel0, div.toclevel1, div.toclevel2, div.toclevel3, div.toclevel4 {
 360   margin-top: 0;
 361   margin-bottom: 0;
 362 }
 363 div.toclevel2 {
 364   margin-left: 2em;
 365   font-size: 0.9em;
 366 }
 367 div.toclevel3 {
 368   margin-left: 4em;
 369   font-size: 0.9em;
 370 }
 371 div.toclevel4 {
 372   margin-left: 6em;
 373   font-size: 0.9em;
 374 }
 375
 376 span.aqua { color: aqua; }
 377 span.black { color: black; }
 378 span.blue { color: blue; }
 379 span.fuchsia { color: fuchsia; }
 380 span.gray { color: gray; }
 381 span.green { color: green; }
 382 span.lime { color: lime; }
 383 span.maroon { color: maroon; }
 384 span.navy { color: navy; }
 385 span.olive { color: olive; }
 386 span.purple { color: purple; }
 387 span.red { color: red; }
 388 span.silver { color: silver; }
 389 span.teal { color: teal; }
 390 span.white { color: white; }
 391 span.yellow { color: yellow; }
 392
 393 span.aqua-background { background: aqua; }
 394 span.black-background { background: black; }
 395 span.blue-background { background: blue; }
 396 span.fuchsia-background { background: fuchsia; }
 397 span.gray-background { background: gray; }
 398 span.green-background { background: green; }
 399 span.lime-background { background: lime; }
 400 span.maroon-background { background: maroon; }
 401 span.navy-background { background: navy; }
 402 span.olive-background { background: olive; }
 403 span.purple-background { background: purple; }
 404 span.red-background { background: red; }
 405 span.silver-background { background: silver; }
 406 span.teal-background { background: teal; }
 407 span.white-background { background: white; }
 408 span.yellow-background { background: yellow; }
 409
 410 span.big { font-size: 2em; }
 411 span.small { font-size: 0.6em; }
 412
 413 span.underline { text-decoration: underline; }
 414 span.overline { text-decoration: overline; }
 415 span.line-through { text-decoration: line-through; }
 416
 417 div.unbreakable { page-break-inside: avoid; }
 418
 419
 420 /*
 421  * xhtml11 specific
 422  *
 423  * */
 424
 425 div.tableblock {
 426   margin-top: 1.0em;
 427   margin-bottom: 1.5em;
 428 }
 429 div.tableblock > table {
 430   border: 3px solid #527bbd;
 431 }
 432 thead, p.table.header {
 433   font-weight: bold;
 434   color: #527bbd;
 435 }
 436 p.table {
 437   margin-top: 0;
 438 }
 439 /* Because the table frame attribute is overridden by CSS in most browsers. */
 440 div.tableblock > table[frame="void"] {
 441   border-style: none;
 442 }
 443 div.tableblock > table[frame="hsides"] {
 444   border-left-style: none;
 445   border-right-style: none;
 446 }
 447 div.tableblock > table[frame="vsides"] {
 448   border-top-style: none;
 449   border-bottom-style: none;
 450 }
 451
 452
 453 /*
 454  * html5 specific
 455  *
 456  * */
 457
 458 table.tableblock {
 459   margin-top: 1.0em;
 460   margin-bottom: 1.5em;
 461 }
 462 thead, p.tableblock.header {
 463   font-weight: bold;
 464   color: #527bbd;
 465 }
 466 p.tableblock {
 467   margin-top: 0;
 468 }
 469 table.tableblock {
 470   border-width: 3px;
 471   border-spacing: 0px;
 472   border-style: solid;
 473   border-color: #527bbd;
 474   border-collapse: collapse;
 475 }
 476 th.tableblock, td.tableblock {
 477   border-width: 1px;
 478   padding: 4px;
 479   border-style: solid;
 480   border-color: #527bbd;
 481 }
 482
 483 table.tableblock.frame-topbot {
 484   border-left-style: hidden;
 485   border-right-style: hidden;
 486 }
 487 table.tableblock.frame-sides {
 488   border-top-style: hidden;
 489   border-bottom-style: hidden;
 490 }
 491 table.tableblock.frame-none {
 492   border-style: hidden;
 493 }
 494
 495 th.tableblock.halign-left, td.tableblock.halign-left {
 496   text-align: left;
 497 }
 498 th.tableblock.halign-center, td.tableblock.halign-center {
 499   text-align: center;
 500 }
 501 th.tableblock.halign-right, td.tableblock.halign-right {
 502   text-align: right;
 503 }
 504
 505 th.tableblock.valign-top, td.tableblock.valign-top {
 506   vertical-align: top;
 507 }
 508 th.tableblock.valign-middle, td.tableblock.valign-middle {
 509   vertical-align: middle;
 510 }
 511 th.tableblock.valign-bottom, td.tableblock.valign-bottom {
 512   vertical-align: bottom;
 513 }
 514
 515
 516 /*
 517  * manpage specific
 518  *
 519  * */
 520
 521 body.manpage h1 {
 522   padding-top: 0.5em;
 523   padding-bottom: 0.5em;
 524   border-top: 2px solid silver;
 525   border-bottom: 2px solid silver;
 526 }
 527 body.manpage h2 {
 528   border-style: none;
 529 }
 530 body.manpage div.sectionbody {
 531   margin-left: 3em;
 532 }
 533
 534 @media print {
 535   body.manpage div#toc { display: none; }
 536 }
 537
 538
 539 </style>
 540 <script type="text/javascript">
 541 /*<![CDATA[*/
 542 var asciidoc = {  // Namespace.
 543
 544 /////////////////////////////////////////////////////////////////////
 545 // Table Of Contents generator
 546 /////////////////////////////////////////////////////////////////////
 547
 548 /* Author: Mihai Bazon, September 2002
 549  * http://students.infoiasi.ro/~mishoo
 550  *
 551  * Table Of Content generator
 552  * Version: 0.4
 553  *
 554  * Feel free to use this script under the terms of the GNU General Public
 555  * License, as long as you do not remove or alter this notice.
 556  */
 557
 558  /* modified by Troy D. Hanson, September 2006. License: GPL */
 559  /* modified by Stuart Rackham, 2006, 2009. License: GPL */
 560
 561 // toclevels = 1..4.
 562 toc: function (toclevels) {
 563
 564   function getText(el) {
 565     var text = "";
 566     for (var i = el.firstChild; i != null; i = i.nextSibling) {
 567       if (i.nodeType == 3 /* Node.TEXT_NODE */) // IE doesn't speak constants.
 568         text += i.data;
 569       else if (i.firstChild != null)
 570         text += getText(i);
 571     }
 572     return text;
 573   }
 574
 575   function TocEntry(el, text, toclevel) {
 576     this.element = el;
 577     this.text = text;
 578     this.toclevel = toclevel;
 579   }
 580
 581   function tocEntries(el, toclevels) {
 582     var result = new Array;
 583     var re = new RegExp('[hH]([1-'+(toclevels+1)+'])');
 584     // Function that scans the DOM tree for header elements (the DOM2
 585     // nodeIterator API would be a better technique but not supported by all
 586     // browsers).
 587     var iterate = function (el) {
 588       for (var i = el.firstChild; i != null; i = i.nextSibling) {
 589         if (i.nodeType == 1 /* Node.ELEMENT_NODE */) {
 590           var mo = re.exec(i.tagName);
 591           if (mo && (i.getAttribute("class") || i.getAttribute("className")) != "float") {
 592             result[result.length] = new TocEntry(i, getText(i), mo[1]-1);
 593           }
 594           iterate(i);
 595         }
 596       }
 597     }
 598     iterate(el);
 599     return result;
 600   }
 601
 602   var toc = document.getElementById("toc");
 603   if (!toc) {
 604     return;
 605   }
 606
 607   // Delete existing TOC entries in case we're reloading the TOC.
 608   var tocEntriesToRemove = [];
 609   var i;
 610   for (i = 0; i < toc.childNodes.length; i++) {
 611     var entry = toc.childNodes[i];
 612     if (entry.nodeName.toLowerCase() == 'div'
 613      && entry.getAttribute("class")
 614      && entry.getAttribute("class").match(/^toclevel/))
 615       tocEntriesToRemove.push(entry);
 616   }
 617   for (i = 0; i < tocEntriesToRemove.length; i++) {
 618     toc.removeChild(tocEntriesToRemove[i]);
 619   }
 620
 621   // Rebuild TOC entries.
 622   var entries = tocEntries(document.getElementById("content"), toclevels);
 623   for (var i = 0; i < entries.length; ++i) {
 624     var entry = entries[i];
 625     if (entry.element.id == "")
 626       entry.element.id = "_toc_" + i;
 627     var a = document.createElement("a");
 628     a.href = "#" + entry.element.id;
 629     a.appendChild(document.createTextNode(entry.text));
 630     var div = document.createElement("div");
 631     div.appendChild(a);
 632     div.className = "toclevel" + entry.toclevel;
 633     toc.appendChild(div);
 634   }
 635   if (entries.length == 0)
 636     toc.parentNode.removeChild(toc);
 637 },
 638
 639
 640 /////////////////////////////////////////////////////////////////////
 641 // Footnotes generator
 642 /////////////////////////////////////////////////////////////////////
 643
 644 /* Based on footnote generation code from:
 645  * http://www.brandspankingnew.net/archive/2005/07/format_footnote.html
 646  */
 647
 648 footnotes: function () {
 649   // Delete existing footnote entries in case we're reloading the footnodes.
 650   var i;
 651   var noteholder = document.getElementById("footnotes");
 652   if (!noteholder) {
 653     return;
 654   }
 655   var entriesToRemove = [];
 656   for (i = 0; i < noteholder.childNodes.length; i++) {
 657     var entry = noteholder.childNodes[i];
 658     if (entry.nodeName.toLowerCase() == 'div' && entry.getAttribute("class") == "footnote")
 659       entriesToRemove.push(entry);
 660   }
 661   for (i = 0; i < entriesToRemove.length; i++) {
 662     noteholder.removeChild(entriesToRemove[i]);
 663   }
 664
 665   // Rebuild footnote entries.
 666   var cont = document.getElementById("content");
 667   var spans = cont.getElementsByTagName("span");
 668   var refs = {};
 669   var n = 0;
 670   for (i=0; i<spans.length; i++) {
 671     if (spans[i].className == "footnote") {
 672       n++;
 673       var note = spans[i].getAttribute("data-note");
 674       if (!note) {
 675         // Use [\s\S] in place of . so multi-line matches work.
 676         // Because JavaScript has no s (dotall) regex flag.
 677         note = spans[i].innerHTML.match(/\s*\[([\s\S]*)]\s*/)[1];
 678         spans[i].innerHTML =
 679           "[<a id='_footnoteref_" + n + "' href='#_footnote_" + n +
 680           "' title='View footnote' class='footnote'>" + n + "</a>]";
 681         spans[i].setAttribute("data-note", note);
 682       }
 683       noteholder.innerHTML +=
 684         "<div class='footnote' id='_footnote_" + n + "'>" +
 685         "<a href='#_footnoteref_" + n + "' title='Return to text'>" +
 686         n + "</a>. " + note + "</div>";
 687       var id =spans[i].getAttribute("id");
 688       if (id != null) refs["#"+id] = n;
 689     }
 690   }
 691   if (n == 0)
 692     noteholder.parentNode.removeChild(noteholder);
 693   else {
 694     // Process footnoterefs.
 695     for (i=0; i<spans.length; i++) {
 696       if (spans[i].className == "footnoteref") {
 697         var href = spans[i].getElementsByTagName("a")[0].getAttribute("href");
 698         href = href.match(/#.*/)[0];  // Because IE return full URL.
 699         n = refs[href];
 700         spans[i].innerHTML =
 701           "[<a href='#_footnote_" + n +
 702           "' title='View footnote' class='footnote'>" + n + "</a>]";
 703       }
 704     }
 705   }
 706 },
 707
 708 install: function(toclevels) {
 709   var timerId;
 710
 711   function reinstall() {
 712     asciidoc.footnotes();
 713     if (toclevels) {
 714       asciidoc.toc(toclevels);
 715     }
 716   }
 717
 718   function reinstallAndRemoveTimer() {
 719     clearInterval(timerId);
 720     reinstall();
 721   }
 722
 723   timerId = setInterval(reinstall, 500);
 724   if (document.addEventListener)
 725     document.addEventListener("DOMContentLoaded", reinstallAndRemoveTimer, false);
 726   else
 727     window.onload = reinstallAndRemoveTimer;
 728 }
 729
 730 }
 731 asciidoc.install();
 732 /*]]>*/
 733 </script>
 734 </head>
 735 <body class="article">
 736 <div id="header">
 737 <h1>How to recover a corrupted blob object</h1>
 738 <span id="revdate">2024-04-15</span>
 739 </div>
 740 <div id="content">
 741 <div id="preamble">
 742 <div class="sectionbody">
 743 <div class="listingblock">
 744 <div class="content">
 745 <pre><code>On Fri, 9 Nov 2007, Yossi Leybovich wrote:
 746 &gt;
 747 &gt; Did not help still the repository look for this object?
 748 &gt; Any one know how can I track this object and understand which file is it</code></pre>
 749 </div></div>
 750 <div class="paragraph"><p>So exactly <strong>because</strong> the SHA-1 hash is cryptographically secure, the hash
 751 itself doesn&#8217;t actually tell you anything, in order to fix a corrupt
 752 object you basically have to find the "original source" for it.</p></div>
 753 <div class="paragraph"><p>The easiest way to do that is almost always to have backups, and find the
 754 same object somewhere else. Backups really are a good idea, and Git makes
 755 it pretty easy (if nothing else, just clone the repository somewhere else,
 756 and make sure that you do <strong>not</strong> use a hard-linked clone, and preferably
 757 not the same disk/machine).</p></div>
 758 <div class="paragraph"><p>But since you don&#8217;t seem to have backups right now, the good news is that
 759 especially with a single blob being corrupt, these things <strong>are</strong> somewhat
 760 debuggable.</p></div>
 761 <div class="paragraph"><p>First off, move the corrupt object away, and <strong>save</strong> it. The most common
 762 cause of corruption so far has been memory corruption, but even so, there
 763 are people who would be interested in seeing the corruption - but it&#8217;s
 764 basically impossible to judge the corruption until we can also see the
 765 original object, so right now the corrupt object is useless, but it&#8217;s very
 766 interesting for the future, in the hope that you can re-create a
 767 non-corrupt version.</p></div>
 768 <div class="listingblock">
 769 <div class="content">
 770 <pre><code>So:
 771
 772 &gt; ib]$ mv .git/objects/4b/9458b3786228369c63936db65827de3cc06200 ../</code></pre>
 773 </div></div>
 774 <div class="paragraph"><p>This is the right thing to do, although it&#8217;s usually best to save it under
 775 it&#8217;s full SHA-1 name (you just dropped the "4b" from the result ;).</p></div>
 776 <div class="paragraph"><p>Let&#8217;s see what that tells us:</p></div>
 777 <div class="listingblock">
 778 <div class="content">
 779 <pre><code>&gt; ib]$ git-fsck --full
 780 &gt; broken link from    tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
 781 &gt;              to    blob 4b9458b3786228369c63936db65827de3cc06200
 782 &gt; missing blob 4b9458b3786228369c63936db65827de3cc06200</code></pre>
 783 </div></div>
 784 <div class="paragraph"><p>Ok, I removed the "dangling commit" messages, because they are just
 785 messages about the fact that you probably have rebased etc, so they&#8217;re not
 786 at all interesting. But what remains is still very useful. In particular,
 787 we now know which tree points to it!</p></div>
 788 <div class="paragraph"><p>Now you can do</p></div>
 789 <div class="literalblock">
 790 <div class="content">
 791 <pre><code>git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8</code></pre>
 792 </div></div>
 793 <div class="paragraph"><p>which will show something like</p></div>
 794 <div class="literalblock">
 795 <div class="content">
 796 <pre><code>100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8    .gitignore
 797 100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883    .mailmap
 798 100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c    COPYING
 799 100644 blob ee909f2cc49e54f0799a4739d24c4cb9151ae453    CREDITS
 800 040000 tree 0f5f709c17ad89e72bdbbef6ea221c69807009f6    Documentation
 801 100644 blob 1570d248ad9237e4fa6e4d079336b9da62d9ba32    Kbuild
 802 100644 blob 1c7c229a092665b11cd46a25dbd40feeb31661d9    MAINTAINERS
 803 ...</code></pre>
 804 </div></div>
 805 <div class="paragraph"><p>and you should now have a line that looks like</p></div>
 806 <div class="literalblock">
 807 <div class="content">
 808 <pre><code>10064 blob 4b9458b3786228369c63936db65827de3cc06200     my-magic-file</code></pre>
 809 </div></div>
 810 <div class="paragraph"><p>in the output. This already tells you a <strong>lot</strong> it tells you what file the
 811 corrupt blob came from!</p></div>
 812 <div class="paragraph"><p>Now, it doesn&#8217;t tell you quite enough, though: it doesn&#8217;t tell what
 813 <strong>version</strong> of the file didn&#8217;t get correctly written! You might be really
 814 lucky, and it may be the version that you already have checked out in your
 815 working tree, in which case fixing this problem is really simple, just do</p></div>
 816 <div class="literalblock">
 817 <div class="content">
 818 <pre><code>git hash-object -w my-magic-file</code></pre>
 819 </div></div>
 820 <div class="paragraph"><p>again, and if it outputs the missing SHA-1 (4b945..) you&#8217;re now all done!</p></div>
 821 <div class="paragraph"><p>But that&#8217;s the really lucky case, so let&#8217;s assume that it was some older
 822 version that was broken. How do you tell which version it was?</p></div>
 823 <div class="paragraph"><p>The easiest way to do it is to do</p></div>
 824 <div class="literalblock">
 825 <div class="content">
 826 <pre><code>git log --raw --all --full-history -- subdirectory/my-magic-file</code></pre>
 827 </div></div>
 828 <div class="paragraph"><p>and that will show you the whole log for that file (please realize that
 829 the tree you had may not be the top-level tree, so you need to figure out
 830 which subdirectory it was in on your own), and because you&#8217;re asking for
 831 raw output, you&#8217;ll now get something like</p></div>
 832 <div class="literalblock">
 833 <div class="content">
 834 <pre><code>commit abc
 835 Author:
 836 Date:
 837   ..
 838 :100644 100644 4b9458b... newsha... M  somedirectory/my-magic-file</code></pre>
 839 </div></div>
 840 <div class="literalblock">
 841 <div class="content">
 842 <pre><code>commit xyz
 843 Author:
 844 Date:</code></pre>
 845 </div></div>
 846 <div class="literalblock">
 847 <div class="content">
 848 <pre><code>  ..
 849 :100644 100644 oldsha... 4b9458b... M   somedirectory/my-magic-file</code></pre>
 850 </div></div>
 851 <div class="paragraph"><p>and this actually tells you what the <strong>previous</strong> and <strong>subsequent</strong> versions
 852 of that file were! So now you can look at those ("oldsha" and "newsha"
 853 respectively), and hopefully you have done commits often, and can
 854 re-create the missing my-magic-file version by looking at those older and
 855 newer versions!</p></div>
 856 <div class="paragraph"><p>If you can do that, you can now recreate the missing object with</p></div>
 857 <div class="literalblock">
 858 <div class="content">
 859 <pre><code>git hash-object -w &lt;recreated-file&gt;</code></pre>
 860 </div></div>
 861 <div class="paragraph"><p>and your repository is good again!</p></div>
 862 <div class="paragraph"><p>(Btw, you could have ignored the fsck, and started with doing a</p></div>
 863 <div class="literalblock">
 864 <div class="content">
 865 <pre><code>git log --raw --all</code></pre>
 866 </div></div>
 867 <div class="paragraph"><p>and just looked for the sha of the missing object (4b9458b..) in that
 868 whole thing. It&#8217;s up to you - Git does <strong>have</strong> a lot of information, it is
 869 just missing one particular blob version.</p></div>
 870 <div class="paragraph"><p>Trying to recreate trees and especially commits is <strong>much</strong> harder. So you
 871 were lucky that it&#8217;s a blob. It&#8217;s quite possible that you can recreate the
 872 thing.</p></div>
 873 <div class="literalblock">
 874 <div class="content">
 875 <pre><code>Linus</code></pre>
 876 </div></div>
 877 </div>
 878 </div>
 879 </div>
 880 <div id="footnotes"><hr /></div>
 881 <div id="footer">
 882 <div id="footer-text">
 883 Last updated
 884  2024-04-15 14:40:56 PDT
 885 </div>
 886 </div>
 887 </body>
 888 </html>