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403 <body>
405 <h1>
406 gitdiffcore(7) Manual Page
407 </h1>
410 <p>gitdiffcore -
411 Tweaking diff output
412 </p>
413 </div>
414 </div>
420 </div></div>
421 </div>
424 <div class="paragraph"><p>The diff commands <em>git diff-index</em>, <em>git diff-files</em>, and <em>git diff-tree</em>
425 can be told to manipulate differences they find in
427 is collectively called "diffcore transformation". This short note
429 that is easier to understand than the conventional kind.</p></div>
430 </div>
433 <div class="paragraph"><p>The <em>git diff-*</em> family works by first comparing two sets of
434 files:</p></div>
436 <li>
437 <p>
441 used);
442 </p>
443 </li>
444 <li>
445 <p>
447 working directory;
448 </p>
449 </li>
450 <li>
451 <p>
453 </p>
454 </li>
455 </ul></div>
457 the two sets of files by any pathspecs given on their command-lines,
458 and compare corresponding paths in the two resulting sets of files.</p></div>
459 <div class="paragraph"><p>The pathspecs are used to limit the world diff operates in. They remove
460 the filepairs outside the specified sets of pathnames. E.g. If the
461 input set of filepairs included:</p></div>
465 </div></div>
466 <div class="paragraph"><p>but the command invocation was <tt>git diff-files myfile</tt>, then the
467 junkfile entry would be removed from the list because only "myfile"
468 is under consideration.</p></div>
470 internally called "diffcore", in a format similar to what is output
471 when the -p option is not used. E.g.</p></div>
478 </div></div>
480 (each of which is called "filepair", although at this point each
481 of them talks about a single file), and transforms such a list
484 <li>
485 <p>
486 diffcore-break
487 </p>
488 </li>
489 <li>
490 <p>
491 diffcore-rename
492 </p>
493 </li>
494 <li>
495 <p>
496 diffcore-merge-broken
497 </p>
498 </li>
499 <li>
500 <p>
501 diffcore-pickaxe
502 </p>
503 </li>
504 <li>
505 <p>
506 diffcore-order
507 </p>
508 </li>
509 </ul></div>
510 <div class="paragraph"><p>These are applied in sequence. The set of filepairs <em>git diff-*</em>
511 commands find are used as the input to diffcore-break, and
512 the output from diffcore-break is used as the input to the
513 next transformation. The final result is then passed to the
514 output routine and generates either diff-raw format (see Output
516 diff-patch format.</p></div>
517 </div>
518 <h2 id="_diffcore_break_for_splitting_up_complete_rewrites">diffcore-break: For Splitting Up "Complete Rewrites"</h2>
522 used to detect a filepair that represents "complete rewrite" and
523 break such filepair into two filepairs that represent delete and
524 create. E.g. If the input contained this filepair:</p></div>
528 </div></div>
530 it changes it to:</p></div>
535 </div></div>
537 the extent of changes between the contents of the files before
538 and after modification (i.e. the contents that have "bcd1234…"
539 and "0123456…" as their SHA1 content ID, in the above
540 example). The amount of deletion of original contents and
541 insertion of new material are added together, and if it exceeds
542 the "break score", the filepair is broken into two. The break
543 score defaults to 50% of the size of the smaller of the original
544 and the result (i.e. if the edit shrinks the file, the size of
545 the result is used; if the edit lengthens the file, the size of
546 the original is used), and can be customized by giving a number
548 </div>
549 <h2 id="_diffcore_rename_for_detection_renames_and_copies">diffcore-rename: For Detection Renames and Copies</h2>
552 controlled by the -M option (to detect renames) and the -C option
554 input contained these filepairs:</p></div>
559 </div></div>
561 the contents of the created file file0, then rename detection
562 merges these filepairs and creates:</p></div>
566 </div></div>
567 <div class="paragraph"><p>When the "-C" option is used, the original contents of modified files,
568 and deleted files (and also unmodified files, if the
569 "--find-copies-harder" option is used) are considered as candidates
570 of the source files in rename/copy operation. If the input were like
571 these filepairs, that talk about a modified file fileY and a newly
572 created file file0:</p></div>
577 </div></div>
579 file0 are compared, and if they are similar enough, they are
580 changed to:</p></div>
585 </div></div>
587 algorithm used in diffcore-break is used to determine if two
588 files are "similar enough", and can be customized to use
589 a similarity score different from the default of 50% by giving a
594 diffcore mechanism as well as modified ones. This lets the copy
595 detector consider unmodified files as copy source candidates at
598 copied happened to have been modified in the same changeset.</p></div>
599 </div>
600 <h2 id="_diffcore_merge_broken_for_putting_complete_rewrites_back_together">diffcore-merge-broken: For Putting "Complete Rewrites" Back Together</h2>
603 diffcore-break, and not transformed into rename/copy by
604 diffcore-rename, back into a single modification. This always
605 runs when diffcore-break is used.</p></div>
607 different "extent of changes" computation from the ones used by
608 diffcore-break and diffcore-rename. It counts only the deletion
609 from the original, and does not count insertion. If you removed
611 new lines to make a new 1000-line document, you did not do a
612 complete rewrite. diffcore-break breaks such a case in order to
613 help diffcore-rename to consider such filepairs as candidate of
614 rename/copy detection, but if filepairs broken that way were not
615 matched with other filepairs to create rename/copy, then this
616 transformation merges them back into the original
620 material is deleted, the broken pairs are merged back into a
621 single modification) by giving a second number to -B option,
622 like these:</p></div>
624 <li>
625 <p>
627 for diffcore-merge-broken).
628 </p>
629 </li>
630 <li>
631 <p>
633 </p>
634 </li>
635 </ul></div>
637 creation and deletion patches. This was an unnecessary hack and
638 the latest implementation always merges all the broken pairs
639 back into modifications, but the resulting patch output is
640 formatted differently for easier review in case of such
641 a complete rewrite by showing the entire contents of old version
644 </div>
645 <h2 id="_diffcore_pickaxe_for_detecting_addition_deletion_of_specified_string">diffcore-pickaxe: For Detecting Addition/Deletion of Specified String</h2>
648 changes that touch a specified string, and is controlled by the
650 commands.</p></div>
653 different number of specified string. Such a filepair represents
654 "the string appeared in this changeset". It also checks for the
655 opposite case that loses the specified string.</p></div>
657 only such filepairs that touch the specified string in its
659 filepairs intact if there is such a filepair, or makes the
660 output empty otherwise. The latter behaviour is designed to
661 make reviewing of the changes in the context of the whole
662 changeset easier.</p></div>
663 </div>
664 <h2 id="_diffcore_order_for_sorting_the_output_based_on_filenames">diffcore-order: For Sorting the Output Based on Filenames</h2>
667 (or project’s) taste, and is controlled by the -O option to the
670 pattern. Filepairs that match a glob pattern on an earlier line
671 in the file are output before ones that match a later line, and
672 filepairs that do not match any glob pattern are output last.</p></div>
674 would look like this:</p></div>
677 <pre><tt>README
678 Makefile
679 Documentation
680 *.h
681 *.c
682 t</tt></pre>
683 </div></div>
684 </div>
695 </div>
699 </div>
703 </div>
704 </div>
705 </body>
706 </html>