Feature: new mbtiles diff command

docs/src/mbtiles-diff.md

@@ -0,0 +1,16 @@
+# Diffing MBTiles
+
+## `mbtiles diff`
+
+Diff command compares two mbtiles files `file A` and `file B`, and generates a delta (diff) file. If the diff file
+is [applied](mbtiles-copy.md#mbtiles-apply-patch) to `A`, it will produce `B`.  
+The delta file will contain all tiles that are different between the two files (modifications, insertions, and deletions
+as `NULL` values), for both the tile and metadata tables.  
+The only exception is `agg_tiles_has` metadata value. It will be renamed to `agg_tiles_hash_in_diff` and a
+new `agg_tiles_hash` will be generated for the diff file itself.
+
+```shell
+# This command will comapre `file_a.mbtiles` and `file_b.mbtiles`, and generate a new diff file `diff_result.mbtiles`,This command will compares file_a.mbtiles and file_b.mbtiles, and generates a new diff file diff_result.mbtiles 
+# If the diff file is applied to file_a, it will produce file_b. 
+mbtiles diff file_a.mbtiles file_b.mbtiles diff_result.mbtiles
+```

mbtiles/src/bin/mbtiles.rs

@@ -52,6 +52,13 @@ enum Commands {
         /// Value to set, or nothing if the key should be deleted.
         value: Option<String>,
     },
+    /// Compare two files A and B, and generate a new diff file. If the diff file is applied to A, it will produce B.
+    #[command(name = "diff")]
+    Diff {
+        file_a: PathBuf,
+        file_b: PathBuf,
+        diff: PathBuf,
+    },
     /// Copy tiles from one mbtiles file to another.
     #[command(name = "copy", alias = "cp")]
     Copy(CopyArgs),
@@ -212,6 +219,28 @@ async fn main_int() -> anyhow::Result<()> {
             println!("MBTiles file summary for {mbt}");
             println!("{}", mbt.summary(&mut conn).await?);
         }
+        Commands::Diff {
+            file_a,
+            file_b,
+            diff,
+        } => {
+            let opts = MbtilesCopier {
+                src_file: file_a,
+                diff_with_file: Some(file_b),
+                dst_file: diff,
+                copy: CopyType::All,
+                skip_agg_tiles_hash: false,
+                on_duplicate: Some(CopyDuplicateMode::Override),
+                dst_type_cli: None,
+                dst_type: None,
+                min_zoom: None,
+                max_zoom: None,
+                zoom_levels: vec![],
+                bbox: vec![],
+                apply_patch: None,
+            };
+            opts.run().await?;
+        }
     }
 
     Ok(())
@@ -253,7 +282,7 @@ mod tests {
     use mbtiles::CopyDuplicateMode;
 
     use super::*;
-    use crate::Commands::{ApplyPatch, Copy, MetaGetValue, MetaSetValue, Validate};
+    use crate::Commands::{ApplyPatch, Copy, Diff, MetaGetValue, MetaSetValue, Validate};
     use crate::{Args, IntegrityCheckType};
 
     #[test]
@@ -524,4 +553,29 @@ mod tests {
             }
         );
     }
+
+    #[test]
+    fn test_diff() {
+        let file_a = PathBuf::from("../tests/fixtures/mbtiles/geography-class-jpg.mbtiles");
+        let file_b = PathBuf::from("file:copy_with_diff_with_file_mem_db?mode=memory&cache=shared");
+
+        let diff = PathBuf::from("../tests/fixtures/mbtiles/geography-class-jpg-modified.mbtiles");
+        assert_eq!(
+            Args::parse_from([
+                "mbtiles",
+                "diff",
+                file_a.to_str().unwrap(),
+                file_b.to_str().unwrap(),
+                diff.to_str().unwrap()
+            ]),
+            Args {
+                verbose: false,
+                command: Diff {
+                    file_a,
+                    file_b,
+                    diff,
+                }
+            }
+        );
+    }
 }