git/t/lib-diff-alternative.sh
John Cai a4cf900ee7 diff: teach diff to read algorithm from diff driver
It can be useful to specify diff algorithms per file type. For example,
one may want to use the minimal diff algorithm for .json files, another
for .c files, etc.

The diff machinery already checks attributes for a diff driver. Teach
the diff driver parser a new type "algorithm" to look for in the
config, which will be used if a driver has been specified through the
attributes.

Enforce precedence of the diff algorithm by favoring the command line
option, then looking at the driver attributes & config combination, then
finally the diff.algorithm config.

To enforce precedence order, use a new `ignore_driver_algorithm` member
during options parsing to indicate the diff algorithm was set via command
line args.

Signed-off-by: John Cai <johncai86@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-02-21 09:29:10 -08:00

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# Helpers shared by the test scripts for diff algorithms (patience,
# histogram, etc).
test_diff_frobnitz() {
cat >file1 <<\EOF
#include <stdio.h>
// Frobs foo heartily
int frobnitz(int foo)
{
int i;
for(i = 0; i < 10; i++)
{
printf("Your answer is: ");
printf("%d\n", foo);
}
}
int fact(int n)
{
if(n > 1)
{
return fact(n-1) * n;
}
return 1;
}
int main(int argc, char **argv)
{
frobnitz(fact(10));
}
EOF
cat >file2 <<\EOF
#include <stdio.h>
int fib(int n)
{
if(n > 2)
{
return fib(n-1) + fib(n-2);
}
return 1;
}
// Frobs foo heartily
int frobnitz(int foo)
{
int i;
for(i = 0; i < 10; i++)
{
printf("%d\n", foo);
}
}
int main(int argc, char **argv)
{
frobnitz(fib(10));
}
EOF
file1=$(git rev-parse --short $(git hash-object file1))
file2=$(git rev-parse --short $(git hash-object file2))
cat >expect <<EOF
diff --git a/file1 b/file2
index $file1..$file2 100644
--- a/file1
+++ b/file2
@@ -1,26 +1,25 @@
#include <stdio.h>
+int fib(int n)
+{
+ if(n > 2)
+ {
+ return fib(n-1) + fib(n-2);
+ }
+ return 1;
+}
+
// Frobs foo heartily
int frobnitz(int foo)
{
int i;
for(i = 0; i < 10; i++)
{
- printf("Your answer is: ");
printf("%d\n", foo);
}
}
-int fact(int n)
-{
- if(n > 1)
- {
- return fact(n-1) * n;
- }
- return 1;
-}
-
int main(int argc, char **argv)
{
- frobnitz(fact(10));
+ frobnitz(fib(10));
}
EOF
cat >expect_diffstat <<EOF
file1 => file2 | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
EOF
STRATEGY=$1
test_expect_success "$STRATEGY diff from attributes" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --no-index file1 file2 > output &&
cat expect &&
cat output &&
test_cmp expect output
'
test_expect_success "$STRATEGY diff from attributes has valid diffstat" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --stat --no-index file1 file2 > output &&
test_cmp expect_diffstat output
'
test_expect_success "$STRATEGY diff" '
test_must_fail git diff --no-index "--diff-algorithm=$STRATEGY" file1 file2 > output &&
test_cmp expect output
'
test_expect_success "$STRATEGY diff command line precedence before attributes" '
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm myers &&
test_must_fail git diff --no-index "--diff-algorithm=$STRATEGY" file1 file2 > output &&
test_cmp expect output
'
test_expect_success "$STRATEGY diff attributes precedence before config" '
git config diff.algorithm default &&
echo "file* diff=driver" >.gitattributes &&
git config diff.driver.algorithm "$STRATEGY" &&
test_must_fail git diff --no-index file1 file2 > output &&
test_cmp expect output
'
test_expect_success "$STRATEGY diff output is valid" '
mv file2 expect &&
git apply < output &&
test_cmp expect file2
'
}
test_diff_unique() {
cat >uniq1 <<\EOF
1
2
3
4
5
6
EOF
cat >uniq2 <<\EOF
a
b
c
d
e
f
EOF
uniq1=$(git rev-parse --short $(git hash-object uniq1))
uniq2=$(git rev-parse --short $(git hash-object uniq2))
cat >expect <<EOF
diff --git a/uniq1 b/uniq2
index $uniq1..$uniq2 100644
--- a/uniq1
+++ b/uniq2
@@ -1,6 +1,6 @@
-1
-2
-3
-4
-5
-6
+a
+b
+c
+d
+e
+f
EOF
STRATEGY=$1
test_expect_success 'completely different files' '
test_must_fail git diff --no-index "--$STRATEGY" uniq1 uniq2 > output &&
test_cmp expect output
'
}