RFR: 8314543: gitattributes: make diffs easier to read

[Andrei Rybak]

Git supports special hunk headers for several languages in diff output, which make it easier to read diffs of files in that language, generated by Git (git-diff, git-show, `git log -p`, etc).  For details, see `git help gitattributes` or [the online documentation](https://git-scm.com/docs/gitattributes).

Add entries to the root .gitattributes file to support showing the hunk headers for Java, C, C++, Markdown, Shell script, HTML, and CSS.  This makes it easier to read diffs generated by Git.

As an example, for j.l.Integer, before, the hunk header just shows the class name, found using the generic hunk header regex:


$ git show --format='' 71ca85f5a6741a2db55a529192564f94b269fbd9 -- src/java.base/share/classes/java/lang/Integer.java
diff --git a/src/java.base/share/classes/java/lang/Integer.java b/src/java.base/share/classes/java/lang/Integer.java
index 7d200e7edf5..9ec9d3941f8 100644
--- a/src/java.base/share/classes/java/lang/Integer.java
+++ b/src/java.base/share/classes/java/lang/Integer.java
@@ -517,13 +517,9 @@ public final class Integer extends Number
         }

         // We know there are at most two digits left at this point.
-        q = i / 10;
-        r = (q * 10) - i;
-        buf[--charPos] = (byte)('0' + r);
-
-        // Whatever left is the remaining digit.
-        if (q < 0) {
-            buf[--charPos] = (byte)('0' - q);
+        buf[--charPos] = DigitOnes[-i];
+        if (i < -9) {
+            buf[--charPos] = DigitTens[-i];
         }

         if (negative) {


After, the hunk shows the method edited by the commit, derived using the regex specific to Java:


$ git show --format='' 71ca85f5a6741a2db55a529192564f94b269fbd9 -- src/java.base/share/classes/java/lang/Integer.java
diff --git a/src/java.base/share/classes/java/lang/Integer.java b/src/java.base/share/classes/java/lang/Integer.java
index 7d200e7edf5..9ec9d3941f8 100644
--- a/src/java.base/share/classes/java/lang/Integer.java
+++ b/src/java.base/share/classes/java/lang/Integer.java
@@ -517,13 +517,9 @@ static int getChars(int i, int index, byte[] buf) {
         }

         // We know there are at most two digits left at this point.
-        q = i / 10;
-        r = (q * 10) - i;
-        buf[--charPos] = (byte)('0' + r);
-
-        // Whatever left is the remaining digit.
-        if (q < 0) {
-            buf[--charPos] = (byte)('0' - q);
+        buf[--charPos] = DigitOnes[-i];
+        if (i < -9) {
+            buf[--charPos] = DigitTens[-i];
         }

         if (negative) {


----

This was [previously discussed](https://mail.openjdk.org/pipermail/skara-dev/2023-August/008108.html) on the skara-dev mailing list.

-------------

Commit messages:
 - gitattributes: make diffs easier to read

Changes: https://git.openjdk.org/jdk/pull/15334/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15334&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314543
  Stats: 9 lines in 1 file changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15334.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15334/head:pull/15334

PR: https://git.openjdk.org/jdk/pull/15334