| git-range-diff(1) | |
| ================= | |
| NAME | |
| ---- | |
| git-range-diff - Compare two commit ranges (e.g. two versions of a branch) | |
| SYNOPSIS | |
| -------- | |
| [verse] | |
| 'git range-diff' [--color=[<when>]] [--no-color] [<diff-options>] | |
| [--no-dual-color] [--creation-factor=<factor>] | |
| ( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> ) | |
| DESCRIPTION | |
| ----------- | |
| This command shows the differences between two versions of a patch | |
| series, or more generally, two commit ranges (ignoring merge commits). | |
| To that end, it first finds pairs of commits from both commit ranges | |
| that correspond with each other. Two commits are said to correspond when | |
| the diff between their patches (i.e. the author information, the commit | |
| message and the commit diff) is reasonably small compared to the | |
| patches' size. See ``Algorithm`` below for details. | |
| Finally, the list of matching commits is shown in the order of the | |
| second commit range, with unmatched commits being inserted just after | |
| all of their ancestors have been shown. | |
| OPTIONS | |
| ------- | |
| --no-dual-color:: | |
| When the commit diffs differ, `git range-diff` recreates the | |
| original diffs' coloring, and adds outer -/+ diff markers with | |
| the *background* being red/green to make it easier to see e.g. | |
| when there was a change in what exact lines were added. | |
| + | |
| Additionally, the commit diff lines that are only present in the first commit | |
| range are shown "dimmed" (this can be overridden using the `color.diff.<slot>` | |
| config setting where `<slot>` is one of `contextDimmed`, `oldDimmed` and | |
| `newDimmed`), and the commit diff lines that are only present in the second | |
| commit range are shown in bold (which can be overridden using the config | |
| settings `color.diff.<slot>` with `<slot>` being one of `contextBold`, | |
| `oldBold` or `newBold`). | |
| + | |
| This is known to `range-diff` as "dual coloring". Use `--no-dual-color` | |
| to revert to color all lines according to the outer diff markers | |
| (and completely ignore the inner diff when it comes to color). | |
| --creation-factor=<percent>:: | |
| Set the creation/deletion cost fudge factor to `<percent>`. | |
| Defaults to 60. Try a larger value if `git range-diff` erroneously | |
| considers a large change a total rewrite (deletion of one commit | |
| and addition of another), and a smaller one in the reverse case. | |
| See the ``Algorithm`` section below for an explanation why this is | |
| needed. | |
| <range1> <range2>:: | |
| Compare the commits specified by the two ranges, where | |
| `<range1>` is considered an older version of `<range2>`. | |
| <rev1>...<rev2>:: | |
| Equivalent to passing `<rev2>..<rev1>` and `<rev1>..<rev2>`. | |
| <base> <rev1> <rev2>:: | |
| Equivalent to passing `<base>..<rev1>` and `<base>..<rev2>`. | |
| Note that `<base>` does not need to be the exact branch point | |
| of the branches. Example: after rebasing a branch `my-topic`, | |
| `git range-diff my-topic@{u} my-topic@{1} my-topic` would | |
| show the differences introduced by the rebase. | |
| `git range-diff` also accepts the regular diff options (see | |
| linkgit:git-diff[1]), most notably the `--color=[<when>]` and | |
| `--no-color` options. These options are used when generating the "diff | |
| between patches", i.e. to compare the author, commit message and diff of | |
| corresponding old/new commits. There is currently no means to tweak the | |
| diff options passed to `git log` when generating those patches. | |
| CONFIGURATION | |
| ------------- | |
| This command uses the `diff.color.*` and `pager.range-diff` settings | |
| (the latter is on by default). | |
| See linkgit:git-config[1]. | |
| EXAMPLES | |
| -------- | |
| When a rebase required merge conflicts to be resolved, compare the changes | |
| introduced by the rebase directly afterwards using: | |
| ------------ | |
| $ git range-diff @{u} @{1} @ | |
| ------------ | |
| A typical output of `git range-diff` would look like this: | |
| ------------ | |
| -: ------- > 1: 0ddba11 Prepare for the inevitable! | |
| 1: c0debee = 2: cab005e Add a helpful message at the start | |
| 2: f00dbal ! 3: decafe1 Describe a bug | |
| @@ -1,3 +1,3 @@ | |
| Author: A U Thor <author@example.com> | |
| -TODO: Describe a bug | |
| +Describe a bug | |
| @@ -324,5 +324,6 | |
| This is expected. | |
| -+What is unexpected is that it will also crash. | |
| ++Unexpectedly, it also crashes. This is a bug, and the jury is | |
| ++still out there how to fix it best. See ticket #314 for details. | |
| Contact | |
| 3: bedead < -: ------- TO-UNDO | |
| ------------ | |
| In this example, there are 3 old and 3 new commits, where the developer | |
| removed the 3rd, added a new one before the first two, and modified the | |
| commit message of the 2nd commit as well its diff. | |
| When the output goes to a terminal, it is color-coded by default, just | |
| like regular `git diff`'s output. In addition, the first line (adding a | |
| commit) is green, the last line (deleting a commit) is red, the second | |
| line (with a perfect match) is yellow like the commit header of `git | |
| show`'s output, and the third line colors the old commit red, the new | |
| one green and the rest like `git show`'s commit header. | |
| A naive color-coded diff of diffs is actually a bit hard to read, | |
| though, as it colors the entire lines red or green. The line that added | |
| "What is unexpected" in the old commit, for example, is completely red, | |
| even if the intent of the old commit was to add something. | |
| To help with that, `range` uses the `--dual-color` mode by default. In | |
| this mode, the diff of diffs will retain the original diff colors, and | |
| prefix the lines with -/+ markers that have their *background* red or | |
| green, to make it more obvious that they describe how the diff itself | |
| changed. | |
| Algorithm | |
| --------- | |
| The general idea is this: we generate a cost matrix between the commits | |
| in both commit ranges, then solve the least-cost assignment. | |
| The cost matrix is populated thusly: for each pair of commits, both | |
| diffs are generated and the "diff of diffs" is generated, with 3 context | |
| lines, then the number of lines in that diff is used as cost. | |
| To avoid false positives (e.g. when a patch has been removed, and an | |
| unrelated patch has been added between two iterations of the same patch | |
| series), the cost matrix is extended to allow for that, by adding | |
| fixed-cost entries for wholesale deletes/adds. | |
| Example: Let commits `1--2` be the first iteration of a patch series and | |
| `A--C` the second iteration. Let's assume that `A` is a cherry-pick of | |
| `2,` and `C` is a cherry-pick of `1` but with a small modification (say, | |
| a fixed typo). Visualize the commits as a bipartite graph: | |
| ------------ | |
| 1 A | |
| 2 B | |
| C | |
| ------------ | |
| We are looking for a "best" explanation of the new series in terms of | |
| the old one. We can represent an "explanation" as an edge in the graph: | |
| ------------ | |
| 1 A | |
| / | |
| 2 --------' B | |
| C | |
| ------------ | |
| This explanation comes for "free" because there was no change. Similarly | |
| `C` could be explained using `1`, but that comes at some cost c>0 | |
| because of the modification: | |
| ------------ | |
| 1 ----. A | |
| | / | |
| 2 ----+---' B | |
| | | |
| `----- C | |
| c>0 | |
| ------------ | |
| In mathematical terms, what we are looking for is some sort of a minimum | |
| cost bipartite matching; `1` is matched to `C` at some cost, etc. The | |
| underlying graph is in fact a complete bipartite graph; the cost we | |
| associate with every edge is the size of the diff between the two | |
| commits' patches. To explain also new commits, we introduce dummy nodes | |
| on both sides: | |
| ------------ | |
| 1 ----. A | |
| | / | |
| 2 ----+---' B | |
| | | |
| o `----- C | |
| c>0 | |
| o o | |
| o o | |
| ------------ | |
| The cost of an edge `o--C` is the size of `C`'s diff, modified by a | |
| fudge factor that should be smaller than 100%. The cost of an edge | |
| `o--o` is free. The fudge factor is necessary because even if `1` and | |
| `C` have nothing in common, they may still share a few empty lines and | |
| such, possibly making the assignment `1--C`, `o--o` slightly cheaper | |
| than `1--o`, `o--C` even if `1` and `C` have nothing in common. With the | |
| fudge factor we require a much larger common part to consider patches as | |
| corresponding. | |
| The overall time needed to compute this algorithm is the time needed to | |
| compute n+m commit diffs and then n*m diffs of patches, plus the time | |
| needed to compute the least-cost assigment between n and m diffs. Git | |
| uses an implementation of the Jonker-Volgenant algorithm to solve the | |
| assignment problem, which has cubic runtime complexity. The matching | |
| found in this case will look like this: | |
| ------------ | |
| 1 ----. A | |
| | / | |
| 2 ----+---' B | |
| .--+-----' | |
| o -' `----- C | |
| c>0 | |
| o ---------- o | |
| o ---------- o | |
| ------------ | |
| SEE ALSO | |
| -------- | |
| linkgit:git-log[1] | |
| GIT | |
| --- | |
| Part of the linkgit:git[1] suite |