Add :start=sha[...] filter

Change: start-filter

src/filter/grammar.pest

@@ -18,6 +18,7 @@ char = {
 
 filter_spec = { (
     filter_group
+  | filter_group_arg
   | filter_presub
   | filter_subdir
   | filter_nop
@@ -26,6 +27,7 @@ filter_spec = { (
 )+ }
 
 filter_group = { CMD_START ~ cmd? ~ GROUP_START ~ compose ~ GROUP_END }
+filter_group_arg = { CMD_START ~ cmd ~ "=" ~ argument ~ GROUP_START ~ compose ~ GROUP_END }
 filter_subdir = { CMD_START ~ "/" ~ argument }
 filter_nop = { CMD_START ~ "/" }
 filter_presub = { CMD_START ~ ":" ~ argument }

src/filter/mod.rs

@@ -98,6 +98,7 @@ enum Op {
     Fold,
     Paths,
     Squash(Option<std::collections::HashMap<git2::Oid, (String, String, String)>>),
+    Start(git2::Oid, Filter),
     Linear,
 
     RegexReplace(regex::Regex, String),
@@ -223,6 +224,9 @@ fn spec2(op: &Op) -> String {
         Op::Exclude(b) => {
             format!(":exclude[{}]", spec(*b))
         }
+        Op::Start(id, b) => {
+            format!(":start={}[{}]", id, spec(*b))
+        }
         Op::Workspace(path) => {
             format!(":workspace={}", parse::quote(&path.to_string_lossy()))
         }
@@ -374,6 +378,14 @@ fn apply_to_commit2(
             ))
             .transpose()
         }
+        Op::Start(id,filter) => {
+            if *id == commit.id() {
+                return apply_to_commit2(&to_op(*filter), commit, transaction);
+            } else {
+
+                return apply_to_commit2(&Op::Nop, commit, transaction);
+            }
+        },
         _ => {
             if let Some(oid) = transaction.get(filter, commit.id()) {
                 return Ok(Some(oid));
@@ -619,6 +631,7 @@ fn apply2<'a>(
         Op::Squash(None) => Ok(tree),
         Op::Squash(Some(_)) => Err(josh_error("not applicable to tree")),
         Op::Linear => Ok(tree),
+        Op::Start(_,_) => Err(josh_error("not applicable to tree")),
 
         Op::RegexReplace(regex, replacement) => {
             tree::regex_replace(tree.id(), &regex, &replacement, transaction)

src/filter/opt.rs

@@ -328,6 +328,7 @@ fn step(filter: Filter) -> Filter {
                 Op::Prefix(path)
             }
         }
+        Op::Start(id, filter) => Op::Start(id, step(filter)),
         Op::Compose(filters) if filters.is_empty() => Op::Empty,
         Op::Compose(filters) if filters.len() == 1 => to_op(filters[0]),
         Op::Compose(mut filters) => {

src/filter/parse.rs

@@ -103,6 +103,20 @@ fn parse_item(pair: pest::iterators::Pair<Rule>) -> JoshResult<Op> {
                 _ => Err(josh_error("parse_item: no match {:?}")),
             }
         }
+        Rule::filter_group_arg => {
+            let v: Vec<_> = pair.into_inner().map(|x| unquote(x.as_str())).collect();
+
+            match v.as_slice() {
+                [cmd, arg, args] => {
+                    let g = parse_group(args)?;
+                    match *cmd {
+                        "start" => Ok(Op::Start(git2::Oid::from_str(arg)?, to_filter(Op::Compose(g)))),
+                        _ => Err(josh_error("parse_item: no match")),
+                    }
+                }
+                _ => Err(josh_error("parse_item: no match {:?}")),
+            }
+        }
         _ => Err(josh_error("parse_item: no match")),
     }
 }

tests/filter/start.t

@@ -0,0 +1,49 @@
+  $ export RUST_BACKTRACE=1
+  $ git init -q 1> /dev/null
+
+  $ echo contents1 > file1
+  $ git add .
+  $ git commit -m "add file1" 1> /dev/null
+
+  $ git log --graph --pretty=%s
+  * add file1
+
+  $ git checkout -b branch2
+  Switched to a new branch 'branch2'
+
+  $ echo contents2 > file1
+  $ git add .
+  $ git commit -m "mod file1" 1> /dev/null
+
+  $ echo contents3 > file3
+  $ git add .
+  $ git commit -m "mod file3" 1> /dev/null
+
+  $ git checkout master
+  Switched to branch 'master'
+
+  $ echo contents3 > file2
+  $ git add .
+  $ git commit -m "add file2" 1> /dev/null
+
+  $ git merge -q branch2 --no-ff
+
+  $ git log --graph --pretty=%H
+  *   1d69b7d2651f744be3416f2ad526aeccefb99310
+  |\  
+  | * 86871b8775ad3baca86484337d1072aa1d386f7e
+  | * 975d4c4975912729482cc864d321c5196a969271
+  * | e707f76bb6a1390f28b2162da5b5eb6933009070
+  |/  
+  * 0b4cf6c9efbbda1eada39fa9c1d21d2525b027bb
+
+  $ josh-filter -s :start=0b4cf6c9efbbda1eada39fa9c1d21d2525b027bb[:prefix=x] --update refs/heads/filtered
+
+  $ git log --graph --decorate --pretty=%H refs/heads/filtered
+  *   1d69b7d2651f744be3416f2ad526aeccefb99310
+  |\  
+  | * 86871b8775ad3baca86484337d1072aa1d386f7e
+  | * 975d4c4975912729482cc864d321c5196a969271
+  * | e707f76bb6a1390f28b2162da5b5eb6933009070
+  |/  
+  * 0b4cf6c9efbbda1eada39fa9c1d21d2525b027bb