Implement an advanced fuzzy diffing feature for interdiff

Makefile.am

@@ -432,7 +432,21 @@ TESTS = tests/newline1/run-test \
 	tests/git-deleted-file/run-test \
 	tests/git-pure-rename/run-test \
 	tests/git-diff-edge-cases/run-test \
-	tests/malformed-diff-headers/run-test
+	tests/malformed-diff-headers/run-test \
+	tests/fuzzy1/run-test \
+	tests/fuzzy2/run-test \
+	tests/fuzzy3/run-test \
+	tests/fuzzy4/run-test \
+	tests/fuzzy5/run-test \
+	tests/fuzzy6/run-test \
+	tests/fuzzy7/run-test \
+	tests/fuzzy8/run-test \
+	tests/fuzzy9/run-test \
+	tests/fuzzy10/run-test \
+	tests/fuzzy11/run-test \
+	tests/fuzzy12/run-test \
+	tests/fuzzy13/run-test \
+	tests/fuzzy14/run-test
 
 # Scanner tests (only when scanner-patchfilter is enabled)
 if USE_SCANNER_PATCHFILTER

README.md → README

@@ -57,20 +57,60 @@ Patchutils is a small collection of programs that operate on patch files. It pro
 
 - **svndiff** / **svndiffview** - Subversion-specific diff viewing tools.
 
-## Installation
-
-Patchutils uses the standard GNU autotools build system:
+## Building from the Git repository
 
 ```bash
+./gnulib-update.sh
+./bootstrap
 ./configure
-make
+make -j$(nproc)
+```
+
+The `gnulib-update.sh` and `./bootstrap` steps are only needed once
+(or when `configure.ac` / `Makefile.am` change). After that, just
+`./configure && make` is sufficient.
+
+This requires **automake**, **autoconf**, and **gnulib-devel** to be
+installed on your system.
+
+## Installation
+
+```bash
 make install
 ```
 
-## Building from the Git repository
+## Testing
+
+```bash
+make check
+```
+
+Run a single test:
+
+```bash
+make check TESTS=tests/addhunk1/run-test
+```
+
+### Stress-testing fuzzy mode
+
+The `tests/stress-test-fuzzy.sh` script mass-tests `interdiff --fuzzy`
+by comparing every commit in a git range against itself. Since both
+inputs are identical, any output from interdiff indicates a bug. This
+is effective against any git repository, but large repositories like
+the Linux kernel are particularly useful because they exercise a wide
+variety of patch shapes: hunks at line 1 with no pre-context, files
+ending without a newline, file creations and deletions, mode-only
+changes, multi-thousand-line diffs, whitespace-damaged patches, hunks
+with duplicate context lines, and so on.
+
+```bash
+INTERDIFF=./src/interdiff ./tests/stress-test-fuzzy.sh /path/to/linux v2.6.12-rc2..v6.19
+```
 
-After cloning the source from GitHub, run `./bootstrap` to generate the `configure` script.
-This step requires **automake**, **autoconf**, and **gnulib-devel** to be installed on your system.
+Only commits that produce non-empty output, a non-zero exit code, or a
+timeout are printed. The `JOBS`, `TIMEOUT`, and `INTERDIFF` environment
+variables can be used to tune parallelism, per-commit timeout (default
+30s), and the interdiff binary path respectively.
 
 ## Requirements