largefiles: use strip() instead of slicing to get rid of EOL of standin This slicing prevents from replacing SHA-1 by another (= longer hash value) in the future.

largefiles: rename local variable appropriately repo['.'] is called not as "working context" but as "parent context". In this code path, hash value of current content of file should be compared against hash value recorded in "parent context". Therefore, "wctx" may cause misunderstanding in this case.

largefiles: avoid redundant loop to eliminate None from list Before this patch, this code path contains two loops for m._files: one for replacement with standin, and another for elimination of None, which comes from previous replacement ("standin in wctx or lfdirstate[f] == 'r'" case in tostandin()). These two loops can be unified into simple one "for" loop.

largefiles: avoid meaningless changectx looking up Logically, "repo[ctx.node()]" should be equal to "ctx". In addition to it, this redundant code path is repeated "len(match.m_files)" times.

largefiles: avoid redundant changectx looking up at each repetitions These code paths look up changectx at each repetitions, even though the changectx key isn't changed while loop.

largefiles: omit updating newly added standin at linear merging Updating standin for newly added largefile is needed, only if same name largefile exists in destination context at linear merging. In such case, updated standin is used to detect divergence of largefile at overridefilemerge(). Otherwise, standin doesn't have any responsibility for its content (usually, it is empty).

largefiles: reuse hexsha1() to centralize hash calculation logic into it This patch also renames argument of hexsha1(), not only for readability ("data" isn't good name for file-like object), but also for reviewability (including hexsha1() code helps reviewers to confirm how these functions are similar). BTW, copyandhash() has also similar logic, but it can't reuse hexsha1(), because it writes read-in data into specified fileobj simultaneously.