Hi Junio, On Thu, 17 Jun 2021, Junio C Hamano wrote: > "Johannes Schindelin via GitGitGadget" <gitgitgadget@xxxxxxxxx> > writes: > > > From: Johannes Schindelin <johannes.schindelin@xxxxxx> > > > > Since https://github.com/gwsw/less/commit/bb0ee4e76c2, `less` prefers > > the `COLUMNS` variable over asking ncurses itself. > > > > This is typically not a problem because we ask `TIOCGWINSZ` in Git, to > > determine the correct value for `COLUMNS`, and then set that environment > > variable. > > > > However, on Windows it _is_ a problem. The reason is that Git for > > Windows uses a version of `less` that relies on the MSYS2 runtime to > > interact with the pseudo terminal (typically inside a MinTTY window, > > which is also aware of the MSYS2 runtime). Both MinTTY and `less.exe` > > interact with that pseudo terminal via `ioctl()` calls (which the MSYS2 > > runtime emulates even if there is no such thing on Windows). > > > > But `git.exe` itself is _not_ aware of the MSYS2 runtime, or for that > > matter of that pseudo terminal, and has no way to call `ioctl()` or > > `TIOCGWINSZ`. > > > > Therefore, `git.exe` will fall back to hard-coding 80 columns, no matter > > what the actual terminal size is. > > > > But `less.exe` is totally able to interact with the MSYS2 runtime and > > would not actually require Git's help (which actually makes things > > worse here). So let's not override `COLUMNS` on Windows. > > > > Note: we do this _only_ on Windows, and _only_ if `TIOCGWINSZ` is not > > defined, to reduce any potential undesired fall-out from this patch. > > > > This fixes https://github.com/git-for-windows/git/issues/3235 > > > > Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx> > > --- > > pager: do not unnecessarily set COLUMNS on Windows > > > > A recent upgrade of the "less" package in Git for Windows causes > > problems. Here is a work-around. > > > > Changes since v1: > > > > * The commit message was reworded to clarify the underlying issue > > better. > > Thanks for an updated log message to clarify the problem > description. > > I think treating this as "less" specific band-aid is OK, but I do > not think tying this to Windows is a good design choice. > > The guiding principle for this change is more like "if we do not > know and cannot learn the true value, internally assuming 80-columns > as a last resort fallback may be OK, but do not export it for > consumption for other people---they cannot tell if COLUMNS=80 they > see us export is because we actually measured the terminal width and > know it to be 80, or we just punted and used a fallback default", I > think, and there is nothing Windows-specific in there, no? > > In other words, if we use something like the attached as a "less > specific band-aid" for now (i.e. direct replacement of your patch to > fix the specific 'less' problem), and then later clean it up by > actually returning -1 (or -80) from term_columns() as "we do not > know" (or "we do not know---use the negation of this value as > default"), we can help not just this paticular caller you touched, > but all other callers of term_columns(), to make a more intelligent > decision in the future if they wanted to. The root of the issue I > think is because term_columns() does not give callers to tell if its > returned value is merely a guess. That approach should also work. Do you want me to take custody of your patch and issue a v3? If yes, I will mark you as co-author because the patch is not really only mine any longer. Ciao, Dscho > > pager.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git c/pager.c w/pager.c > index 3d37dd7ada..52f27a6765 100644 > --- c/pager.c > +++ w/pager.c > @@ -11,6 +11,10 @@ > static struct child_process pager_process = CHILD_PROCESS_INIT; > static const char *pager_program; > > +/* Is the value coming back from term_columns() just a guess? */ > +static int term_columns_guessed; > + > + > static void close_pager_fds(void) > { > /* signal EOF to pager */ > @@ -114,7 +118,8 @@ void setup_pager(void) > { > char buf[64]; > xsnprintf(buf, sizeof(buf), "%d", term_columns()); > - setenv("COLUMNS", buf, 0); > + if (!term_columns_guessed) > + setenv("COLUMNS", buf, 0); > } > > setenv("GIT_PAGER_IN_USE", "true", 1); > @@ -158,15 +163,20 @@ int term_columns(void) > return term_columns_at_startup; > > term_columns_at_startup = 80; > + term_columns_guessed = 1; > > col_string = getenv("COLUMNS"); > - if (col_string && (n_cols = atoi(col_string)) > 0) > + if (col_string && (n_cols = atoi(col_string)) > 0) { > term_columns_at_startup = n_cols; > + term_columns_guessed = 0; > + } > #ifdef TIOCGWINSZ > else { > struct winsize ws; > - if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_col) > + if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_col) { > term_columns_at_startup = ws.ws_col; > + term_columns_guessed = 0; > + } > } > #endif > >
