Document hasAllInfo

If this documentation is inaccurate in any way please do not hesitate to suggest corrections.

My understanding of this function is strictly from reading the source code and some limited experience implementing fetchers.

src/libfetchers/fetchers.hh

@@ -63,6 +63,11 @@ public:
        one that contains a commit hash or content hash. */
     bool isLocked() const { return locked; }
 
+    /* Check whether the input carries all necessary info required
+       for cache insertion and substitution.
+       These fields are used to uniquely identify cached trees
+       within the "tarball TTL" window without necessarily
+       indicating that the input's origin is unchanged. */
     bool hasAllInfo() const;
 
     bool operator ==(const Input & other) const;