conflict: Move constants to new file `resolve.go`

The conflicts package defines two functions on the `File` structure,
i.e. `Parse` and `Resolve`. The two functions are tied to the `File`
structure which is tied to the Git2Go implementation.

In the upcoming commits we'll introduce a new standalone `Resolve`
function which is not tied to `File` structure, this allows us to
deprecate the `File` structure along with Git2Go:ResolveConflict
deprecation.

Let's move some of the variables which will be common to a new file
`resolve.go`, which would make it easier to deprecate the entire
`parser.go` file in the future.

2 files changed, 73 insertions, 44 deletions

diff --git a/internal/git/conflict/parser.go b/internal/git/conflict/parser.go
index 9a8997afd..b106f8599 100644
--- a/internal/git/conflict/parser.go
+++ b/internal/git/conflict/parser.go
@@ -14,33 +14,6 @@ import (
 	"strings"
 )
 
-// Errors that can occur during parsing of a merge conflict file
-var (
-	ErrUnmergeableFile     = errors.New("merging is not supported for file")
-	ErrUnexpectedDelimiter = errors.New("unexpected conflict delimiter")
-	ErrMissingEndDelimiter = errors.New("missing last delimiter")
-)
-
-type section uint
-
-const (
-	sectionNone = section(iota)
-	sectionOld
-	sectionNew
-	sectionNoNewline
-)
-
-const fileLimit = 200 * (1 << 10) // 200k
-
-type line struct {
-	objIndex uint // where are we in the object?
-	oldIndex uint // where are we in the old file?
-	newIndex uint // where are we in the new file?
-
-	payload string // actual line contents (minus the newline)
-	section section
-}
-
 // File contains an ordered list of lines with metadata about potential
 // conflicts.
 type File struct {
@@ -54,23 +27,6 @@ func (f File) sectionID(l line) string {
 	return fmt.Sprintf("%x_%d_%d", pathSHA1, l.oldIndex, l.newIndex)
 }
 
-// Resolution indicates how to resolve a conflict
-type Resolution struct {
-	OldPath string `json:"old_path"`
-	NewPath string `json:"new_path"`
-
-	// key is a sectionID, value is "head" or "origin"
-	Sections map[string]string `json:"sections"`
-
-	// Content is used when no sections are defined
-	Content string `json:"content"`
-}
-
-const (
-	head   = "head"
-	origin = "origin"
-)
-
 // Resolve will iterate through each conflict line and replace it with the
 // specified resolution
 func (f File) Resolve(resolution Resolution) ([]byte, error) {
diff --git a/internal/git/conflict/resolve.go b/internal/git/conflict/resolve.go
new file mode 100644
index 000000000..db380fad8
--- /dev/null
+++ b/internal/git/conflict/resolve.go
@@ -0,0 +1,73 @@
+package conflict
+
+import (
+	"errors"
+)
+
+// section denotes the various conflict sections
+type section uint
+
+const (
+	// Resolutions for conflict is done by clients providing selections for
+	// the different conflict sections. "head"/"origin" is used to denote the
+	// selection for ours/their trees respectively.
+	head   = "head"
+	origin = "origin"
+
+	// fileLimit is used to set the limit on the buffer size for bufio.Scanner,
+	// we don't support conflict resolution for files which require bigger buffers.
+	fileLimit = 200 * (1 << 10)
+)
+
+const (
+	// The sections are used to define various lines of the conflicted file.
+	// Here Old/New is used to denote ours/their respectively.
+	sectionNone = section(iota)
+	sectionOld
+	sectionNew
+	sectionNoNewline
+)
+
+// Errors that can occur during parsing of a merge conflict file
+var (
+	// ErrUnmergeableFile is returned when the either the file exceeds the
+	// fileLimit or no data was read from the file (in case of a binary file).
+	ErrUnmergeableFile = errors.New("merging is not supported for file")
+	// ErrUnexpectedDelimiter is returned  when the previous section doesn't
+	// match the expected flow of sections.
+	ErrUnexpectedDelimiter = errors.New("unexpected conflict delimiter")
+	// ErrMissingEndDelimiter is returned when the final section parsed doesn't
+	// match the expected end state.
+	ErrMissingEndDelimiter = errors.New("missing last delimiter")
+)
+
+// line is a structure used to denote individual lines in the conflicted blob,
+// with information around how that line maps to ours/theirs blobs.
+type line struct {
+	// objIndex states the cursor position in the conflicted blob
+	objIndex uint
+	// oldIndex states the cursor position in the 'ours' blob
+	oldIndex uint
+	// oldIndex states the cursor position in the 'theirs' blob
+	newIndex uint
+	// payload denotes the content of line (sans the newline)
+	payload string
+	// section denotes which section this line belongs to.
+	section section
+}
+
+// Resolution indicates how to resolve a conflict
+type Resolution struct {
+	// OldPath is the mapping of the path wrt to 'ours' OID
+	OldPath string `json:"old_path"`
+	// OldPath is the mapping of the path wrt to 'their' OID
+	NewPath string `json:"new_path"`
+
+	// Sections is a map which is used to denote which section to select
+	// for each conflict. Key is the sectionID, while the value is either
+	// "head" or "origin", which denotes the ours/theirs OIDs respectively.
+	Sections map[string]string `json:"sections"`
+
+	// Content is used when no sections are defined
+	Content string `json:"content"`
+}