diff options
Diffstat (limited to 'third_party/git/contrib/diff-highlight/README')
| -rw-r--r-- | third_party/git/contrib/diff-highlight/README | 223 |
1 files changed, 0 insertions, 223 deletions
diff --git a/third_party/git/contrib/diff-highlight/README b/third_party/git/contrib/diff-highlight/README deleted file mode 100644 index d4c234317520..000000000000 --- a/third_party/git/contrib/diff-highlight/README +++ /dev/null @@ -1,223 +0,0 @@ -diff-highlight -============== - -Line oriented diffs are great for reviewing code, because for most -hunks, you want to see the old and the new segments of code next to each -other. Sometimes, though, when an old line and a new line are very -similar, it's hard to immediately see the difference. - -You can use "--color-words" to highlight only the changed portions of -lines. However, this can often be hard to read for code, as it loses -the line structure, and you end up with oddly formatted bits. - -Instead, this script post-processes the line-oriented diff, finds pairs -of lines, and highlights the differing segments. It's currently very -simple and stupid about doing these tasks. In particular: - - 1. It will only highlight hunks in which the number of removed and - added lines is the same, and it will pair lines within the hunk by - position (so the first removed line is compared to the first added - line, and so forth). This is simple and tends to work well in - practice. More complex changes don't highlight well, so we tend to - exclude them due to the "same number of removed and added lines" - restriction. Or even if we do try to highlight them, they end up - not highlighting because of our "don't highlight if the whole line - would be highlighted" rule. - - 2. It will find the common prefix and suffix of two lines, and - consider everything in the middle to be "different". It could - instead do a real diff of the characters between the two lines and - find common subsequences. However, the point of the highlight is to - call attention to a certain area. Even if some small subset of the - highlighted area actually didn't change, that's OK. In practice it - ends up being more readable to just have a single blob on the line - showing the interesting bit. - -The goal of the script is therefore not to be exact about highlighting -changes, but to call attention to areas of interest without being -visually distracting. Non-diff lines and existing diff coloration is -preserved; the intent is that the output should look exactly the same as -the input, except for the occasional highlight. - -Use ---- - -You can try out the diff-highlight program with: - ---------------------------------------------- -git log -p --color | /path/to/diff-highlight ---------------------------------------------- - -If you want to use it all the time, drop it in your $PATH and put the -following in your git configuration: - ---------------------------------------------- -[pager] - log = diff-highlight | less - show = diff-highlight | less - diff = diff-highlight | less ---------------------------------------------- - - -Color Config ------------- - -You can configure the highlight colors and attributes using git's -config. The colors for "old" and "new" lines can be specified -independently. There are two "modes" of configuration: - - 1. You can specify a "highlight" color and a matching "reset" color. - This will retain any existing colors in the diff, and apply the - "highlight" and "reset" colors before and after the highlighted - portion. - - 2. You can specify a "normal" color and a "highlight" color. In this - case, existing colors are dropped from that line. The non-highlighted - bits of the line get the "normal" color, and the highlights get the - "highlight" color. - -If no "new" colors are specified, they default to the "old" colors. If -no "old" colors are specified, the default is to reverse the foreground -and background for highlighted portions. - -Examples: - ---------------------------------------------- -# Underline highlighted portions -[color "diff-highlight"] -oldHighlight = ul -oldReset = noul ---------------------------------------------- - ---------------------------------------------- -# Varying background intensities -[color "diff-highlight"] -oldNormal = "black #f8cbcb" -oldHighlight = "black #ffaaaa" -newNormal = "black #cbeecb" -newHighlight = "black #aaffaa" ---------------------------------------------- - - -Using diff-highlight as a module --------------------------------- - -If you want to pre- or post- process the highlighted lines as part of -another perl script, you can use the DiffHighlight module. You can -either "require" it or just cat the module together with your script (to -avoid run-time dependencies). - -Your script may set up one or more of the following variables: - - - $DiffHighlight::line_cb - this should point to a function which is - called whenever DiffHighlight has lines (which may contain - highlights) to output. The default function prints each line to - stdout. Note that the function may be called with multiple lines. - - - $DiffHighlight::flush_cb - this should point to a function which - flushes the output (because DiffHighlight believes it has completed - processing a logical chunk of input). The default function flushes - stdout. - -The script may then feed lines, one at a time, to DiffHighlight::handle_line(). -When lines are done processing, they will be fed to $line_cb. Note that -DiffHighlight may queue up many input lines (to analyze a whole hunk) -before calling $line_cb. After providing all lines, call -DiffHighlight::flush() to flush any unprocessed lines. - -If you just want to process stdin, DiffHighlight::highlight_stdin() -is a convenience helper which will loop and flush for you. - - -Bugs ----- - -Because diff-highlight relies on heuristics to guess which parts of -changes are important, there are some cases where the highlighting is -more distracting than useful. Fortunately, these cases are rare in -practice, and when they do occur, the worst case is simply a little -extra highlighting. This section documents some cases known to be -sub-optimal, in case somebody feels like working on improving the -heuristics. - -1. Two changes on the same line get highlighted in a blob. For example, - highlighting: - ----------------------------------------------- --foo(buf, size); -+foo(obj->buf, obj->size); ----------------------------------------------- - - yields (where the inside of "+{}" would be highlighted): - ----------------------------------------------- --foo(buf, size); -+foo(+{obj->buf, obj->}size); ----------------------------------------------- - - whereas a more semantically meaningful output would be: - ----------------------------------------------- --foo(buf, size); -+foo(+{obj->}buf, +{obj->}size); ----------------------------------------------- - - Note that doing this right would probably involve a set of - content-specific boundary patterns, similar to word-diff. Otherwise - you get junk like: - ------------------------------------------------------ --this line has some -{i}nt-{ere}sti-{ng} text on it -+this line has some +{fa}nt+{a}sti+{c} text on it ------------------------------------------------------ - - which is less readable than the current output. - -2. The multi-line matching assumes that lines in the pre- and post-image - match by position. This is often the case, but can be fooled when a - line is removed from the top and a new one added at the bottom (or - vice versa). Unless the lines in the middle are also changed, diffs - will show this as two hunks, and it will not get highlighted at all - (which is good). But if the lines in the middle are changed, the - highlighting can be misleading. Here's a pathological case: - ------------------------------------------------------ --one --two --three --four -+two 2 -+three 3 -+four 4 -+five 5 ------------------------------------------------------ - - which gets highlighted as: - ------------------------------------------------------ --one --t-{wo} --three --f-{our} -+two 2 -+t+{hree 3} -+four 4 -+f+{ive 5} ------------------------------------------------------ - - because it matches "two" to "three 3", and so forth. It would be - nicer as: - ------------------------------------------------------ --one --two --three --four -+two +{2} -+three +{3} -+four +{4} -+five 5 ------------------------------------------------------ - - which would probably involve pre-matching the lines into pairs - according to some heuristic. |